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DE C A E L O 



BY 



J. L. ^TOCKS, M.A., D.S.O. 

FELLOW AND TUTOR OF ST- JOHN'S COLLEGE, OXFORD 



OXFORD 

AT THE CLARENDON PRESS 

1922 






A^^i 



Oxford University Press 

London Edinburgh Glasgotu Copenhagen 

Neiu York Toronto Melkourtie Cape Toivn 

Bombay Calcutta Madras Shanghai 
Humphrey Milford Publisher to the Univeesity 






PREFACE 

This translation was begun many years ago in co-opera- 
tion with Mr. H. B. Wallis of the Board of Education. 
Unfortunately he was obliged to turn to other work, but 
his original draft formed the basis of nearly half my 
version of the book. 

Rather full textual notes are given throughout, the text 
of Prantl being taken as basis. (A complete table of the 
passages dealt with will be found in the Index, s.v. Text.) 
For this purpose I have collated the Vienna MS., J, from 
a photograph, and the reading of this MS. is noted in each 
case, either explicitly or by implication. 

Mr. Ross's generous conception of an editor's responsi- 
bilities has been of the greatest service. He has saved me 
from many mistakes and has made many useful suggestions 
for the improvement of the translation. A few of his 
suggestions will be found recorded in the foot-notes as his ; 
but for the most part he is merged in his translator. 

J. L. S. 
3 1 J/ March, 1922. 



CONTENTS 

BOOK I. OF THE HEAVENLY BODIES 

CH. PAGE 

1. The subject of inquiry 268* 

2. That in addition to the four elements, earth, water, air, and 

fire, there is a fifth element, the movement of which is 
circular 268^^ 

3. That this body is exempt from alteration ana decay . . 269^ 

4. That the circular movement has no contrary . . . 270^ 

5. That no body is infinite.— (i) Not the primary body, or fifth 

element 271^ 

6. (ii) None of the other elements 273^ 

7. (iii) In general, an infinite body is impossible . . . 274* 

8. That there cannot be more than one Heaven. — (i) Proved 

from a consideration of the natural movements and places 

of the elements 276* 

9. (ii) Proved by the principles of form and matter, the three 

different senses of .the term ' heaven ' being explained. 
Corollary. — There is no place or void or time outside the 
Heaven 277^ 

10. That the Heaven is ungenerated and indestructible. — 

(i) Review of previous theories 279^^ 

11. (ii) Definition of the terms 'ungenerated' and 'indestructible', 

and of their opposites . . . . . . • 280^ 

12. (iii) Proof of the thesis 281^ 



BOOK II. OF THE HEAVENLY BODIES {continued) 

1. Corroboration of this result 283'* 

2. Of the sense in which the spatial oppositions, up and down, 

right and left, can be attributed to the Heaven . . 284^ 

3. Why there is a plurality of movements and of bodies within 

the Heaven 286* 

4. That the Heaven is perfectly spherical .... 286^ 

5. Why the first Heaven revolves in one direction rather than 

the other 287^ 

6. That the movement of the first Heaven is regular . . 288=^ 

7. Of the stars. — (i) That they are not composed of fire . . 289^ 

8. (ii) That their movement is due to the movement of circles 

to which they are attached 289^^ 

9. (iii) That no 'harmony of the spheres' results from their 

movement 290^ 

10. (iv) Of their order 291^ 



vi CONTENTS 

CH. PAGE 

11. (v) Of their spherical shape 291*' 

12. (vi) Solution of two problems concerning their order and 

movements .291^ 

13. Of the Earth.— (i) Review of previous theories . . . 293* 

14. (ii) That it is at rest at the centre, and spherical in shape . 295* 



BOOK III. OF THE SUBLUNARY BODIES 

1. Previous theories concerning generation stated ; the analysis 

of bodies into planes refuted 298=^ 

2. That every simple body possesses a natural movement ; that 

this movement is either upward or downward ; how un- 
natural movement occurs. General results concerning 
generation .......... 300* 

3. Of bodies subject to generation. — (i) What the elements are 302* 

4. (ii) That the elements are limited in number ; the view of 

Leucippus and Democritus refuted . . . . . 302^ 

5. (iii) That the elements cannot be reduced to one . . . 303^ 

6. (iv) That the elements are not eternal, but are generated 

out of one another ........ 304^ 

7. (v) Of the manner of their generation: theviewof Empedocles 

and the explanation by planes refuted . . . .305* 

8. (vi) Refutation of the attempt to differentiate the elements 

by their shapes 306* 



BOOK IV. OF THE SUBLUNARY BODIES {continued) 

1. Of the meaning of the terms ' heavy ' and ' light ' . . 307^ 

2. Review of previous theories concerning these . . . 308^ 

3. Explanation of the variety of motions exhibited by the 

elements 310^ 

4. Of the distinctive constitution and properties of the four 

elements . . .311* 

5. In what sense the matter of which the elements are com- 

posed may be regarded as one 312'^ 

6. That the shape of a body cannot account for the direction, 

but only for the pace, of its movement .... 313''' 



DE CARLO 

BOOK I 

I The science which has to do with nature clearly concerns 268^ 
itself for the most part with bodies and magnitudes and 
their properties and movements, but also with the principles 
of this sort of substance, as many as they may be. For of 
things constituted by nature some are bodies and magni- 5 
tudes, some possess body and magnitude/ and some are 
principles of things which possess these.^ Now a continuum 
is that which is divisible into parts always capable oi" sub- 
division, and a body is that which is every way divisible. 
A magnitude if divisible one way is a line, if two ways 
a surface, and if three a body. Beyond these there is no 
other magnitude, because the three dimensions are all that 10 
there are, and that which is divisible in three directions is 
divisible in all. For, as the Pythagoreans say, the world 
and all that is in it is determined by the number three, 
since beginning and middle and end give the number 
of an ' all ', and the number they give is the triad. And 
so, having taken these three ^ from nature as (so to speak) 
laws of it, we make further use of the number three in the 15 
worship of the Gods."^ Further, we use the terms in 
practice in this way. Of two things, or men, we say * both ', 
but not ' air : three is the first number to which the term 
' all ' has been appropriated.^ And in this, as we have said, 
we do but follow the lead which nature gives. Therefore, -o 
since ' every ' and ' all ' and * complete ' do not differ from 
one another in respect of form, but only, if at all,^ in their 

^ i. e. animate things, such as plants and animals. 

'^ e.g. matter and form, movement, or, in the case of living things, 
soul. 

^ Viz. beginning, middle, and end. 

* Oaths, for instance, usually appeal to three Gods, as in the 
Homeric appeal to Zeus, Athene, and Apollo (Prantl). 

■' Reading elXfjcfiafxev with E and Prantl. The other MSS. have 

4)aiiev (FLM) or KaTu(f)afji.fv (HJ). 

® Reading etVep npa with FHiMJ. 

645-20 • B 



268^ DE CAELO 

matter and in that to which they are applied, body alone 
among magnitudes can be complete. For it alone is de- 
termined by the three dimensions, that is, is an ' all '.^ 
But if it is divisible in three dimensions it is every way 
25 divisible, while the other magnitudes are divisible in one 
dimension or in two alone : for the divisibility and continuity 
of magnitudes depend upon the number of the dimensions, 
one sort being continuous in one direction, another in two, 
another in all. All magnitudes, then, which are divisible 
are also continuous. Whether we can also say that what- 
30 ever is continuous is divisible does not yet, on our present 
grounds, appear. One thing, however, is clear. We cannot 
268^ pass beyond body to a further kind, as we passed from 
length to surface, and from surface to body. For if we 
could, it would cease to be true that body is complete 
magnitude. We could pass beyond it only in virtue of 
a defect in it ; and that which is complete cannot be 
5 defective, since it has being in every respect.^ Now bodies 
which are classed as parts of the whole ^ are each complete 
according to our formula, since each possesses every dimen- 
sion. But each is determined relatively to that part which 
is next to it by contact, for which reason each of them 
is in a sense many bodies. But the whole of which they are 
parts must necessarily be complete, and thus^ in accordance 
10 with the meaning of the word, have being, not in some 
respects only, but in every respect.'* 

The question as to the nature of the whole, whether it is 2 
infinite in size or limited in its total mass, is a matter for 

^ Body alone is so determined, and only what is so determined is 
a totality (an 'all')- Put a comma, instead of a full stop, after rpiaiv. 
The words tovto 5' fVrt Trav are difficult to interpret. Prantl makes 
Tovro predicate, and trans'ates as though we had to nav instead of ttgi'. 
Simplicius gives no help. 

"^ To be incomplete or defective is to lack being in some respect. 

" i.e. the elements. 

* The 'parts' or elements are bodies, and therefore complete in the 
sense just given to the word. They are, however, only parts, and as 
such limited in their being by the juxtaposition of other parts. This 
suggests a development of the notion of completeness which will make 
the term ' complete ' applicable only to the unrestricted being of the 
whole. 



BOOK I. 2 268^ 

subsequent inquiry.^ We will now speak of those parts of 
the whole which are specifically distinct.^ Let us take 
this as our starting-point. All natural bodies and magni- 15 
tudes we hold to be, as such, capable of locomotion ; for 
nature, we say, is their principle of movement.^ But all 
movement that is in place, all locomotion, as we term it, 
is either straight or circular or a combination of these two, 
which are the only simple movements. And the reason of 
this is that these two, the straight and the circular line, are 20 
the only simple magnitudes. Now revolution about the 
centre is circular motion, while the upward and downward 
m.ovements are in a straight line, * upward ' meaning 
motion away from the centre, and ' downward ' motion 
towards it. All simple motion, then, must be motion 
either away from or towards or about the centre. This 
seems to be in exact accord with what we said above : ^ -5 
as body found its completion in three dimensions, so its 
movement completes itself in three forms. 

Bodies are either simple or compounded of such ; and by 
simple bodies I mean those which possess a principle of 
movement in their own nature, such as fire and earth with 
their kinds, and whatever is akin to them.^ Necessarily, 
then, movements also will be either simple or in some sort 3° 
compound — simple in the case of the simple bodies, com- 269' 
pound in that of the composite — and in the latter case the 
motion will be that of the simple body which prevails in the 
composition. Supposing, then, that there is such a thing as 
simple movement, and that circular movement is an instance 
of it, and that both movement of a simple body is simple and 

^ See c. vii. 

^ i. e. the elements, which represent the ultimate distinctions of kind 
among bodies. 

^ Cf. PJiys. 192^20. 

* Reading rjKoXnvdqKevat Kara Xoyov with all MSS. except E. 

^ Ta TovTcov eibrj ('with their kinds') can hardly mean khids 0/ fire 
and earth (e.g. sandy and stony earth, flame and glowing coal), as 
Simplicius supposes, for there is no variety of movement corresponding 
to this variety of kind. Rather, as Alexander supposes, the phrase is 
a generalizing formula {dvrl rou KadnXou nav nvp . . . Kal KadoXov ttcktuv 
yTjv) : fire and its kind, earth and its kind, and other species of the 
same genus (viz. air and water, and the ' fifth body' of which the stars 
are made). 

B 2 



269^ DE CAELO 

simple movement is of a simple body (for if it is movement 

5 of a compound it will be in virtue of a prevailing simple 
element), then there must necessarily be some simple body 
which revolves naturally and in virtue of its own nature ^ 
with a circular movement. By constraint, of course, it may 
be brought to move with the motion of something else 
di-fiferent from itself, but it cannot so move naturally, since 
there is one sort of movement natural to each of the simple 
bodies. Again, if the unnatural movement is the contrary 

lo of the natural and a thing can have no more than one con- 
trary, it will follow that circular movement, being a simple 
motion, must be unnatural, if it is not natural, to the body 
moved. If then (i) the body, whose movement is circular, 
is fire or some other element, its natural motion must be the 
contrary of the circular motion. But a single thing has 
a single contrary ; and upward and downward motion are 

15 the contraries of one another.^ If, on the other hand, 
(2) the body moving with this circular motion which is 
unnatural to it is something different from the elements, 
there will be some other motion which is natural to it. 
But this cannot be. For if the natural motion is upward, 
it will be fire or air, and if downward, water or earth. 
Further, this circular motion is necessarily/ primary. For the 

20 perfect is naturally prior to the imperfect, and the circle is 
a perfect thing. This cannot be said of any straight line : 
— not of an infinite line ; for, if it were perfect, it would 
have a limit and an end: nor of any finite line; for in 
every case there is something beyond it,^ since any finite 
line can be extended. And so, since the prior movement 

25 belongs to the body which is naturally prior, and circular 
movement is prior to straight, and movement in a straight 
line belongs to simple bodies — fire moving straight upward 
and earthy bodies straight downward towards the centre — 
since this is so, it follows that circular movement also must 



^ Reading (hvtov with all MSS. except E. 

^ Therefore neither of these can be a/so the contrary of circular 
motion. Thus there is ;/<9 simple motion opposed as contrary 10 the 
circular. ' 

' Reading nuawv yaj) ((tti tl €kt(')s {e\TTi is omitted by E alone). 



BOOK I. 2 269* 

be the movement of some simple body.^ For the move- 
ment of composite bodies is, as we said, determined by that 
simple body which preponderates in the composition. 30 
These premises clearly give the conclusion that there is in 
nature some bodily substance other than the formations we 
know, prior to them all and more divine than they. But it 
may also be proved as follows. We may take it that all 
movement is either natural or unnatural, and that the 
movement which is unnatural to one body is natural to 
another — as, for instance, is the case with the upward and 
downward movements, which are natural and unnatural to Zh 
fire and earth respectively. It necessarily follows that 269 
circular movement, being unnatural to these bodies, is the 
natural movement of some other. Further, if, on the one 
hand, circular movement is natural to something, it must 
surely be some simple and primary body which is ordained 
to move with a natural circular motion, as fire is ordained 5 
to fly up and earth down. If, on the other hand, the 
movement of the rotating bodies about the centre is 
unnatural^ it would be remarkable and indeed quite in- 
conceivable that this movement alone should be continuous 
and eternal, being nevertheless contrary to nature. At any 
rate the evidence of all other cases goes to show that it is 
the unnatural which quickest passes away. And so, if, as 10 
some say, the body so moved is fire, this movement is just 
as unnatural to it as downward movement ; for any one can 
see that fire moves in a straigTit line away from the centre. 
On all these grounds, therefore, we may infer with con- 
fidence that the:re is something beyond the bodies that are ^5 
about us on this earth, different and separate from them; 
and that the superior glory of its nature is proportionate to 
its distance from this world of ours.- 

^ From his premises Aristotle is here entitled' to conclude, not 
merely that circular movement is the movement of a simple body, but 
also that it is the movement of a simple body'prior to the other simple 
bodies.^ Prantl therefore inserts Trporepoi; after nvd? and appeals to 
Simplicius's paraphrase for corroboration. Simplicius, however, not 
only does not corroborate the conjecture but actually points out that 
this part of the conclusion is suppressed (oTrep w? (x(i(\)k'i TTnpTJKe). The 
insertion of npoTepcv does not really make the argument any clearer. 

2 Cf. Plato, Phaedo, iii B. 



269^ DE CAELO 

In consequence of what has been said, in part by way of 3 
assumption and in part by way of proof, it is clear that not 

20 every body either possesses lightness or heaviness. As 
a preliminary we must explain in what sense we are using 
the words ' heavy ' and ' light ', sufficiently, at least, for our 
present purpose : ^ we can examine the terms more closely 
later, when we come to consider their essential nature.^ Let 
us then apply the term 'heavy' to that which naturally 
moves towards the centre, and ' light ' to that which moves 
naturally away from the centre. The heaviest thing will be 

25 that which sinks to the bottom of all things that move 
downward, and the lightest that which rises to the surface 
of everything that moves upward. Now, necessarily,^ every- 
thing which moves either up or down possesses lightness or 
heaviness or both — but not both relatively to the same 
thing : for things are heavy and light relatively to one 
another ; air, for instance, is light relatively to water, and 

30 water light relatively to earth. The body, then, which 
moves in a circle cannot possibly possess either heaviness 
or lightness. For neither naturally nor unnaturally can it 
move either towards or away from the centre. Movement 
in a straight line certainly does not belong to it natiLrally^ 
since one sort of movement is, as we saw, appropriate to 
each simple body, and so we should be compelled to identify 

35 it with one of the bodies which move in this way. Suppose, 
then, that the movement is iLunattiraL In that case, if it is 
270^ the downward movement which is unnatural, the upward 
movement will be natural ; and if it is the upvv'ard wiitch is 
unnatural, the downward will be natural. For we decided 
that of contrary movements, if the one is unnatural to any- 
thing, the other will be natural to it. But since the natural 
movement of the whole and of its part — of earth, for in- 
5 stance, as a whole and of a small clod — have one and the 
same direction, it results, in the first place, that this body 
can possess no lightness or heaviness at all (for that would 
mean that it could move by its own nature cither from or 

^ Reading Wavoi'i wf tt/xh- (a)? is omitted by E alone). 

^ 15elovv, 15k. IV, cc. i-iv. 

"' Reading avayKX] 8fj (fie is in F alonej. 



BOOK I. 3 270^ 

towards the centre, which, as we know, is impossible) ; 
and, secondly, that it cannot possibly move in the way 
of locomotion by being forced violently aside in an upward 
or downward direction. For neither naturally nor un- 10 
naturally can it move with any other motion but its own, 
either itself or any part of it, since the reasoning which 
applies to the whole applies also to the part. 

It is equally reasonable to assume that this body will be 
ungenerated and indestructible and exempt from increase 
and alteration, since everything that comes to be comes into 
being from its contrary and in some substrate, and passes 75 
away likewise in a substrate by the action of the contrary 
into the contrary, as we explained in our opening discussions.^ 
Now the motions of contraries are contrary. If then this 
body can have no contrary, because there can be no con- 
trary motion to the circular, nature seems justly to have 20 
exempted from contraries the body which was to be un- 
generated and mdestructible. For it is in contraries that 
generation and decay subsist. Again, that which is subject 
to increase increases upon contact with a kindred body, 
which is resolved into its matter.^ But there is nothing out 25 
of which this body can have been generated.^ And if it is 
exempt from increase and diminution,* the same reasoning 
leads us to suppose that it is also unalterable. For altera- 
tion is movement in respect of quality; and qualitative 
states and dispositions, such as health and disease, do not 
come into being without changes of properties. But all 
natural bodies which change their properties we see to be 30 
subject without exception to increase and diminution. This 
is the case, for instance, with the. bodies of animals and 

^ Phys. I. vii-ix. For the phrase, cf. 311* 12. 

'^ Omitting Ka\ to cpBluov (peivei (1. 23). These words are omitted by 
three representative MSS. (EFJ), are not referred to by Simplicius or 
Themistius, and are an awkward intrusion in the sentence since 
what follows apphes only to increase. For the doctrine, cf. Be Gen. et 
Corr. I. V. 

^ Increase is effected by generation of one kindred body out of 
another. This body has no contrary out of which it can be generated. 
Therefore it cannot increase. 

" Reading acjidiTov with H (so Prantl). All other MSS. have 
acpdapTov ; but the rare acf)dLTov would be easily altered to the commoner 
word.^ Simplicius has acbdnprov, but explains that cfidiais is a kind of 
(p6opd and so acpdapTov may be used for a(j)diTov. 



270^ DE CAELO 

their parts and with vegetable bodies, and similarly also 
with those of the elements. And so, if the body which 
moves with a circular motion cannot admit of increase 

35 or diminution^ it is reasonable to suppose that it is also 
unalterable. 
270^ The reasons why the primary body is eternal and not sub- 
ject to increase or diminution, but unaging and unalterable 
and unmodified, will be clear from what has been said to any 
one who believes in our assumptions. Our theory seems to 
5 confirm experience and to be confirmed by it. For all men 
have some conception of the nature of the gods, and all who 
believe in the existence of gods at all, whether barbarian or 
Greek, agree in allotting the highest place to the deity, 
surely because they suppose that immortal is linked with 
immortal and regard any other supposition as inconceivable. 

10 If then there is, as there certainly is, anything divine, what 
we have just said about the primary bodily substance was 
well said. The mere evidence of the senses is enough to 
convince us of this; at least with human certainty. For in 
the whole range of time past, so far as our inherited records 

15 reach, ^ no change appears to have taken place either in the 
whole scheme of the outermost heaven or in any of its 
proper parts. The common name, too, which has been 
handed down from our distant ancestors even to our own 
day, .seems to show that they conceived of it in the fashion 
which we have been expressing. The same ideas, one must 

20 believe, recur in men's minds not once or twice but again 
and again. And so, implying that the primary body is 
something else beyond earth, fire, air. and water, they gave 
the highest place a name of its own, aitJicr, derived from the 
fact that it ' runs always' ^ for an eternity of time. Anaxa- 

25 goras, however, scandalously misuses this name, taking 
aither as equivalent to fire."' 

It is also clear from what has been said why the number 

' .Simplicius says he 'has beeii told^ that there are written astro- 
nomical records (nfrTpa/a? Ttjinjnfis (wuyix'mTovs) in Egypt for the past 
630,000 years and in Babylon for the past 1,440,000 years, 

^ i.e. <iidij() from nel dtiu. The derivation was suggested by Plato 
(Cra/j'/us, 410 H). 

^ i.e. deriving aWiji) from nWnv. Cf. 1)1-:. III. 302^*4. 



BOOK I. 3 270 

of what we call simple bodies cannot be greater than it is. 
The motion of a simple body must itself be simple, and we 
assert that there are only these two simple motions, the 
circular and the straight, the latter being subdivided into 30 
motion away from and motion towards the centre. 

4 That there is no other form of motion opposed as 
contrary to the circular may be proved in various ways. 
In the first place, there is an obvious tendency to oppose 
the straight line to the circular. For concave and convex 35 
are not only regarded as opposed to one another, but they 271^ 
are also coupled together and treated as a unity in oppo- 
sition to the straight. And so, if there is a contrary 
to circular motion^ motion in a straight line must be re- 
cognized as having the best claim to that name. But the 
two forms of rectilinear motion are opposed to one another 
by reason of their places ; for up and dow^n is a difference 5 
and a contrary opposition in place.^^. Secondly, it may be 
thought that the same reasoning which holds good of the 
rectilinear path applies also to the circular, movement from 
A to B being opposed as contrary to movement from B to 
A. But what is meant is still rectilinear motion. For that is 
limited to a single path, while the circular paths which pass to 
through the same two points are infinite in number.^ Even 
if we are confined to the single semicircle and the opposition 
is between movement from C to D and from D to C along 
that semicircle, the case is no better. For the motion is the 
same as that along the diameter, since we invariably regard 
the distance between two points as the length of the straight 
line which joins them.^ It is no more satisfactory to con- 
struct a circle and treat motion along one semicircle as 15 
contrary to motion along the other. For example, taking 

^ The point of this elliptical argument seems to be that, while the 
generally admitted case of contrary opposition (viz. that of upward 
and downward motion) rests on a contrary opposition of places (viz. 
above and below), no such ground can be suggested for the opposition 
of circular to rectilinear motion. 



Fig. I. ^ ^ 3 YiG. II. 





271^ DE CAELO 

a complete circle, motion from £" to /^ on the semicircle G 
may be opposed to motion from F to ^ on the semicircle 
H} But even supposing these are contraries, it in no way 
follows that the reverse motions on the complete cir- 

20 cumference are contraries. Nor again can motion along 
the circle from ^ to ^ be regarded as the contrary of 
motion from A to C :^ for the motion goes from the same 
point towards the same point, and contrary motion was 
distinguished as motion from a contrary to its contrary.^ 
And even if the motion round a circle is the contrary of the 
reverse motion, one of the two would be ineffective : for 
both move to the same point, because ^ that which moves 

25 in a circle, at whatever point it begins, must necessarily 
pass through all the contrary places alike. (By contrarieties 
of place I mean up and down, back and front, and right 
and left ; and the contrary oppositions of movements are 
determined by those of places.) One of the motions, then, 
would be ineffective, for if the two motions were of equal 
strength,^ there would be no movement either way, and if 

30 one of the two were preponderant, the other would be 
inoperative. So that if both bodies were there, one of 
them, inasmuch as it would not be moving with its own 
movement, would be useless, in the sense in which a shoe 
is useless when it is not worn. But God and nature create 
nothing that has not its use.^ 

1 Fig. III. 




c 

^ Fkys. V. V, 229^21. 

^ Reading on for the en of our MSS. a.fter Simplicius, who had both 
readings before him. 

^ Prantl's alteration of yap into ap' is not needed. The yap refers 
back to the remark 'one of the two would be ineffective'. That 
remark is therefore repeated in the text. 

^ The bearing of this argument is clear if it is remembered that the 
assertion of the existence of a certain movement necessarily involves 
for Aristotle the assertion of the existence of a body which naturally 
exhibits the movement. Similarly the assertion that a movement is 
inoperative involves the assertion that a body is inoperative. 



BOOK I. 5 271^ 

5 This being clear, \vc must go on to consider the questions 271^ 
which remain. First, is there an infinite body, as the 
majority of the ancient philosophers thought, or is this an 
impossibihty ? The decision of this question, either way, is 
not unimportant, but rather all-important, to our search for 5 
the truth.^ It is this problem which has practically always 
been the source of the differences of those who have written 
about nature as a whole. So it has been and so it must 
be ; since the least initial deviation from the truth is 
multiplied later a thousandfold.^ Admit, for instance, the 10 
existence of a minimum magnitude, and you will find that 
the minimum which you have introduced, small as it is, causes 
the greatest truths of mathematics to totter. The reason 
is that a principle is great rather in power than in extent ; 
hence that which was small at the start turns out a giant at 
the end. Now the conception of the infinite possesses this 
power of principles, and indeed in the sphere of quantity 
possesses it in a higher degree than any other conception ; so 15 
that it is in no way absurd or unreasonable that the assump- 
tion that an infinite body exists should be of peculiar 
moment to our inquiry. The infinite, then, we must now 
discuss, opening the whole matter from the beginning. 

Every body is necessarily to be classed either as simple 
or as composite ; ^ the infinite body, therefore, will be either 
simple or composite. But it is clear, further, that if the simple 20 
bodies are finite, the composite must also be finite, since 
that which is composed of bodies finite both in number and 
in magnitude is itself finite in respect of number and 
magnitude : its quantity is in fact the samxC as that of the 
bodies which compose it. What remains for us to consider, 
then, is whether any of the simple bodies can be infinite in 
magnitude, or whether this is impossible. Let us try the 25 
primary body first, and then go on to consider the others. - 

The body which moves in a circle must necessarily be 
finite in every respect, for the following reasons, (i) If the 
body so moving is infinite, the radii drawn from the centre 

^ Reading rrjv n^pl ttjs with FHMJ. The phrase recurs in this form 
in Met. 993** 30. 

^ After Plato, Cratylus, 436 D. 

^ The eVrai of all other MSS. is preferable to E's dvai. 



271^ DE CAELO 

30 will be infinite.^ But the space between infinite radii is 
infinite : and by the space between the radii I mean the 
area outside which no magnitude which is in contact with 
the two lines can be conceived as falling.^ This, I say, will 
be infinite : first, because in the case of finite radii it is always 
272^ finite ; and secondly,^ because in it one can always go on to 
a width greater than any given width ; thus the reasoning 
which forces us to believe in infinite number, because there is 
no maximum, applies also to the space between the radii. 
Now the infinite cannot be traversed, and If the body is 
infinite the interval between the radii is necessarily infinite : 
5 circular motion therefore is an impossibihty. Yet our e.yes 
tell us that the heavens revolve in a circle, and by argument 
also we have determined that there is something to which 
circular movement belongs, 

(2) Again, if from a finite time a finite time be subtracted, 
what remains must be finite and have a beginning. And if 
10 the time of a journey has a beginning, there must be 
a beginning also of the movement, and consequently also 
of the distance traversed. This applies universally. Take 
a line, AC£, infinite in one direction, £, and another line, 
BB, infinite in both directions.* hetACB describe a circle, 

■^ 'The centre', when not in any way qualified, means the centre 
of the earth, which is taken by Aristotle to be also the centre of all the 
revolutions of the heavenly bodies. He cannot here mean the centre 
of the supposed infinite body, since to that no shape has yet been given. 

^ The last phrase {ov fjir]8eu eartv e^w Xn^eh) seems to have been mis- 
understood by Prantl. A comparison of this passage with others in 
which what is practically the same phrase occurs (esp. Mel. 1021^12, 
1055^12) shows {a) that ov is governed by e^o) ('outside which'), and 
(d) that the phrase is roughly equivalent to reXnou. The point here 
is that by didarqiia he means, not a straight line spanning the interval 
between the radii, but the whole area enclosed between the two radii 
and the portion of the circumference which connects their extremities. 
In 1. 30 read, after ^incrTrijxn, hi rather than yai), which is in E alone. 

^ Reading eVt with the MSS. ; Prantl's inei seems to have nothing 
to recommend it. It will then be necessary to put a full-stop after 
dtaarTf]naTos in 1. 3. This sentence gives, of course, a second reason 
for taking the hnaTmia to be infinite. 

* Fig.. IV. ,^ 



-C 

A 



BOOK I. 5 272 

revolving upon C as centre. In its movement it will cut 15 
BB continuously for a certain time. This will be a finite 
time, since the total time is finite in which the heavens 
complete their circular orbit, and consequently the time 
subtracted from it, during which the one line in its motion 
cuts the other, is also finite. Therefore there will be 
a point at which A CE began for the first time to cut BB. 
This, however, is impossible.^ The infinite, then, cannot 
revolve in a circle ; nor could the world, if it were infinite.^ 20 

(3) That the infinite cannot move may also be shown as 
follows. Let A he a finite line m.oving past the finite line, 
B. Of necessity A will pass clear of B and B o( A 3.t the 
same moment ; for each overlaps the other to precisely the 25 
same extent. Now if the two were both moving, and 
moving in contrary directions, they would pass clear of one 
another more rapidly ; if one were still and the other 
moving past it, less rapidly ; provided that the speed of the 
latter were the same in both cases. This, however, is clear : 
that it is impossible to traverse an infinite line in a finite 
time. Infinite time, then, would be required. (This we 30 
demonstrated above in the discussion of movement.^) And 

^ In this argument the ascertained fact that the revolution of the 
heavens occupies a limited time is used to prove the finitude of its 
path and consequently also of the body itself. BB represents an 
infinite line dravi^n within the infinite body and therefore 'traversed' by 
that body in its revolution. But there can be no point at which the 
contact of ACE with BB either begins or ends, while there is a time 
within which the revolution is completed. Therefore the revolving 
body is not infinite. — Possibly the centre of the movement of ACE 
should be A (as in F and Simpl.) rather than C. 

^ Movement of the ' world ' (koV/xo?) is here used for movement of 
the 'heaven' (ovpavos). Either koct/xos- stands for the heavenly body, 
as in Nic. Eth. 1141^ i, or the movement and the infinity are treated 
for the moment as attributes of the whole. 

^ Aristotle refers to the Physics, here and elsewhere, as continuous 
with the De Caelo. Different parts of the Physics are referred to by 
different names. Simplicius (p. 226, 19) observes that Phys. I-IV are 
cited as 'the discussion of principles' (Trept o.py,^v) and Phys. V-VIII 
as 'the discussion of movement' (Trept Kti/jyo-ecus). In Phys. VIII, 
257^34, Aristotle refers back to an earlier passage as occurring eV roiy 

Sokov Tols Trepi (pva^os ; and Simplicius, commenting on this \Coinm. 
in Phys. p. 1233, 30), 'infers' that Phys. I-V are the Trepl (pvaecos and 
Phys. VI-VIII the nepi Kiurjaecos. But his inference is false. The 
reference is not, as he thought, to V. iv. The principle had been 
asserted earlier, viz. in III. i. The ' general considerations concerning 
nature' may therefore be identified with the 'discussion of principles', 
and the Physics may be divided in the middle, i. e. at the end of 
Book IV. — The reference in this passage is to Phys. VI. vii. 



272^ DE CAELO 

it makes no difference whether a finite is passing by an 

272^ infinite or an infinite by a finite. For when A is passing B^ 

then B overlaps ^ A, and it makes no difference whether B 

is moved or unmoved, except that, if both move, they pass 

clear of one another more quickly. It is, however, quite 

possible that a moving line should in certain cases pass one 

which is stationary quicker than it passes one moving in an 

5 opposite direction. One has only to imagine the movement 

to be slow where both move and much faster where one is 

stationary. To suppose one line stationary, then, makes no 

difficulty for our argument, since it is quite possible for A to 

pass ^ at a slower rate when both are moving than when only 

10 one is. If, therefore, the time which the finite moving line 

takes to pass the other is infinite, then necessarily the time 

occupied by the motion of the infinite past the finite is also 

infinite. For the infinite to move at all is thus absolutely 

impossible ; since the very smallest movement conceivable 

must take an infinity of time. Moreover the heavens 

certainly revolve,, and they complete their circular orbit in 

15 a finite time ; so that they pass round the whole extent of 

any line within their orbit, such as the finite line AB. The 

revolving body, therefore, cannot be infinite. 

(4) Again, as a line which has a limit cannot be infinite, 
or, if it is infinite, is so only in length,^ so a surface cannot 

^ Reading KaKdvrj napaWaTTeL eVeiVr/v with FHMJ. The alternative 
to TrnpaWciTTei, Trap', rests upon the sole authority of E : for L has 
7rapa>^\dTTr). Ilap' is intolerable, since it must stand for (/)eperai Trapd 
and thus attributes movement to B, of which in the same sentence it is 
said that it may be unmoved. 

^ The reading is doubtful. It is difficult to attach any other sense 
to the possession of Tiepas ('limit') than a denial of infinity; in which 
case nXX' e'tnep, eVt /LiTjKos means 'or if a finite line is infinite, it is so in 
length'. The antecedent thus appears to contradict both itself and 
the consequent. Simplicius preserves a variant for eVi jxrjKos, firl 
Bdrepa. ('A finite line can only be infinite, if at all, in one direction '.) 
— Perhaps, however, the text is correct. The sentence may be para- 
phrased as follows. A limited line cannot be infinite : lines, in fact, 
can only be infinite, if at all, in that respect in which they are un- 
limited: but there is nothing in the nature of 'line' to determine the 
length of any given line : consequently, it is only in respect to length 
that infinity is ever ascribed to lines. (Mr. Ross suggests that rj should 
be read instead of Jjs in 1. 17. 'A line cannot be infinite in that respect 
in which it is a limit.' The line is the limit of the plane, i. e. a limit 
in respect of breadth. wSimilarly the pU*ne is the limit in respect of 
depth. This correction has support from the translation of Argyropylus 
fex ea parte qua finis est'), and is probably right.) 



BOOK I. 5 



272' 



be infinite in that respect in which it has a limit; or, indeed, 
if it is completely determinate, in any respect whatever. 
Whether it be a square or a circle or a sphere, it cannot be 20 
infinite, any more than a foot-rule can. There is then no 
such thing as an infinite sphere or square or circle, and 
where there is no circle there can be no circular movement, 
and similarly where there is no infinite at all there can be 
no infinite movement ; and from this it follows that, an 
infinite circle being itself an impossibility, there can be no 
circular motion of an infinite body. 

(5) ^^gain, take a centre C, an infinite line, AB, another 25 
infinite line at right angles to it, E^ and a moving radius, 
CD} CD will never cease contact with E^ but the position 
will always be something like CE^ CD cutting E at F,^ 
The infinite line, therefore, refuses to complete the circle.^ 

(6) Again, if the heaven is infinite and moves in a circle, 30 
we shall have to admit that in a finite time it has traversed 
the infinite. For suppose the fixed heaven infinite, and that 
vv^hich moves within it equal to it. It results that when 
the infinite body has completed its revolution, it has 
traversed an infinite equal to itself in a finite time. But 273' 
that we know to be impossible. 

(7) It can also be shown, conversely, that if the time of 
revolution is finite, the area traversed must also be finite: 



^ Also, of course, infinite. 
2 Fig. V. 




^ Tlie 'infinite line' is the infinite radius CD, which is unable to 
complete the circle owing to its inability to extricate its outer extremity 
from that of the other infinite, E. The MSS. vary between kvkXcol 
(EL), kukXco (M), and kvkXov (HFJ : the last, however, has cot supra- 
scriphnn). In FMJ TTepUun follows instead of preceding KVKXnu {kvkXo) 
M). Perhaps kvkXov nepieia-iv should be read with FJ, though either 
reading will give the sense required. 



273^ DE CAELO 

but the area traversed was equal to itself; therefore, it is 
itself finite.^ 
5 We have now shown that the body which moves in 
a circle is not endless or infinite, but has its limit. 

Further, neither that which moves towards nor that 6 
which moves away from the centre can be infinite. For the 
upward and downward motions are contraries and are there- 
fore motions towards contrary places. But if one of a pair 
lo of contraries is determinate, the other must be determinate 

/also. Now the centre is determined ; for, from whatever 
point the body which sinks to the bottom starts its down- 
ward motion, it cannot go farther than the centre. The 
/ centre, therefore, being determinate, the upper place must 

also be determinate. But if these two places are determined 
15 and finite, the corresponding bodies must also be finite. 
Further, if up and down are determinate, the intermediate 
place is also necessarily determinate. For, if it is indeter- 
minate, the movement within it will be infinite ^ ; and 
that we have already shown to be an impossibility.^ The 
middle region then is determinate, and consequently any 
body which either is in it, or might be in it, is determinate. 
20 But the bodies which move up and down may be in it, 
since the one moves naturally away from the centre and 
the other towards it. 

From this alone it is clear that an infinite body is an 
impossibility ; but there is a further point. If there is no 
such thing as infinite weight, then it follows that none of 
these bodies can be infinite. For the supposed infinite 
25 body would have to be infinite in weight. (The same argu- 
ment applies to lightness : for as the one supposition 
involves ^infinite weight, so the infinity of the body which 
rises to the surface involves infinite lightness.) This is 

^ The preceding six arguments start from the hypothesis of an 
infinite body and show the difficulties involved in the consequent 
assumption of an' infinite path and in the infinite time needed for its 
completion. The converse argument starts from known finite time of 
revolution and argues from that to the finitude of the path traversed 
and of liie body which traverses it. 

^ Reading ti'v // ku'tjol; with FHMJ Simpl. 

8 PAj^s. VIII. viii. 



BOOK I. 6 273* 

proved as follows. Assume the weight to be finite, and 
take an infinite body, AB, of the weight C. Subtract from 
the infinite body a finite mass, BD^ the weight of which 30 
shall be E. E then is less than (7, since it is the weight of 
a lesser mass.^ Suppose then that the smaller goes into the 
greater a certain number of times, and take BF bearing 273^ 
the same proportion to BD which the greater weight bears 
to the smaller. For you may subtract as much as you 
please from an infinite. If now the masses are propor- 
tionate to the weights, and the lesser weight is that of the 
lesser mass, the greater must be that of the greater. The 5 
weights, therefore, of the finite and of the infinite body are 
equal. Again, if the weight of a greater body is greater 
than that of a less, the weight of GB will be greater than 
that of FB ; 1 and thus the weight of the finite body is 
greater than that of the infinite. And, further, the weight 
of unequal masses will be the same, since the infinite and 
the finite cannot be equal. It does not matter whether the 10 
weights are commensurable or not. If {a) they are incoin- 
mensurable the same reasoning holds. For instance, 
suppose E multiplied by three is rather more than C\ the 
weight of three masses of the full size oi BD will be greater 
than C. We thus arrive at the same impossibility as 15 
before. Again {b) we may assume weights which are com- 
mensurate ; for it makes no difference whether we begin 
with the weight or with the mass. For example, assume 
the weight E to be commensurate with C, and take from 
the infinite mass a part BD of weight E. Then let a mass 
BF be taken having the same proportion to BD which the 20 
two weights have to one another. (For the mass being 
infinite you may subtract from it as much as you please.) 
These assumed bodies will be commensurate in mass and 
in weight alike. Nor again does it make any difference to 
our demonstration whether the total mass has its weight 
equally or unequally distributed. For it must always be 
possible to take from the infinite mass a body of equal 25 

' FIG. VI. ^ G F O B 

—I 1 1 



273^ DE CAELO 

weight to BD by diminishing or increasing the size of the 
section to the necessary extent.^ 

From what we have said, then, it is clear that the weight 
of the infinite body cannot be finite. It must then be 
infinite. We have therefore only to show this to be im- 
possible in order to prove an infinite body impossible. But 
30 the impossibility of infinite weight can be shown in the 
following way. A given weight moves a given distance in 
a given time ; a weight which is as great and more moves 
the same distance in a less time, the times being in inverse 
274^ proportion to the weights, For instance, if one weight is 
twice another, it will take half as long over a given move- 
ment. Further, a finite weight traverses any finite distance 
in a finite time. It necessarily follows from this that 
infinite weight, if there is such a thing, being, on the one 
5 hand, as great and more than as great as the finite,- will 
move accordingly, but being, on the other hand, compelled 
to move in a time inversely proportionate to its greatness, 
cannot move at all.^ The time should be less in proportion 
as the weight is greater. But there is no proportion be- 
tween the infinite and the finite : proportion can only hold 
between a less and a greater finite time. And though you 
may say that the time of the movement can be continually 
^^ diminished, yet there is no minimum.^ Xor^ if there were, 

^ Delete comma after BA, 

^ There can be no doubt that the conima should follow, not precede, 

Kcii €TL (1. 5). The phrase rocrnvSe oaov TO TTeTTepacT^evov Ka\ ert is 

parallel to the roaoiTov kgl stl of 273^31. Bonitz (Intf. 291^7) takes 
Kni €Ti in this way, but appears to interpret the phrase as indicating 
the distance moved, which is impossible. — For the use of koI en 
cf. J/e/. 1021^6. 

^ Because, as explained in the following sentences, there is no time 
for it to move in. The argument is : the infinite may (nev) be regarded 
loosely as something exceedingly great, in which case it follows simply 
that it moves exceedingly fast : so far there is no difficulty : but (5e') 
as soon as you begin to specify /i07C' great it is and /iorc fast it moves 
the difficulties become insuperable. 

^ aXX' ad iv iXdrrini is probably an opponent's objection. It is 
an application of the argument mentioned in 272*1. We talk of 
number as infinite, A. says there, because there is no maximum. 
Similarly the advocate of infinite weight says, ' At any rate the weight 
can be increased and'the time proportionately diminished ad injinitiim '. 
But the motion of the infinite, to be conceivable, must according to 
Aristotle occupy a //w<?;Jand any time, however small, will be a time 
in which the given movement could be effected by a"finite body. 



BOOK I. 6 274^ 

would it help us. For some finite body could have been 
found greater than the given finite in the same proportion 
which is supposed to hold between the infinite and the 
given finite ;^ so that an infinite and a finite weight must 
have traversed an equal distance in equal time. But that 
is impossible. Again, whatever the time, so long as it is 
finite, in which the infinite performs the motion, a finite 15 
weight must necessarily move a certain finite distance in 
that same time. Infinite weight is therefore impossible, 
and the same reasoning applies also to infinite lightness. 
Bodies then of infinite weight and of infinite lightness are 
equally impossible. 

That there is no infinite body may be shown, as we have 
shown it, by a detailed consideration of the various cases. 20 
But it may also be shown universally, not only by such 
reasoning as we advanced in our discussion of principles ^ 
(though in that passage we have already determined univer- 
sally the sense in which the existence of an infinite is to be 
asserted or denied), but also suitably to our present purpose 
in the following way. That will lead us to a further 
question. Even if the total mass is not infinite, it may 25 
yet be great enough to admit a plurality of universes. The 
question might possibly be raised whether there is any 
obstacle to our believing that there are other universes 
composed on the pattern of our own, more than one, 
though stopping short of infinity. First, however, let us 
treat of the infinite universally. 



^ What difficuhy there is in this sentence is due to the elliptical 
expression and to the tacit inference from a proportion between the 
times to a proportion between the bodies. What is known is the ratio 
between the imaginary minimum time assigned to the infinite body 
and some other finite time. A. speaks of this known ratio as a ratio 
between the infinite body and another body. The argument is : take 
any other finite body (eVepoy) : its ratio to the infinite may be deter- 
mined by their respective times : but another finite body {aXXo ti 
TTenfpaaixevov) could be found in the same ratio (on the basis of 
a comparison of times) to the first. Thus a finite body will cover the 
same distance as the infinite body in the same time, which is absurd. — 
The comma after \6yw in 1. 11 should be deleted, fiet^oi/ belongs to 
the predicate both of the relative clause and of the main sentence. 
Neither Simplicius nor Alexander (as reported by Simplicius) seems 
to have interpreted the words quite correctly. 

^ Phys. III. iv-viii (see n. on 272^ 30). Read elpii^ivovs with FM. 

C 1 



274^ DE CAELO 

30 Every body must necessarily be either finite or infinite, 7 
and if infinite, either of similar or of dissimilar parts. If its 
parts are dissimilar, they must represent either a finite or 
an infinite number of kinds. That the kinds cannot be 
infinite is evident, if our original presuppositions remain 
274^ unchallenged. For the primary movements being finite in 
number, the kinds of simple body are necessarily also finite, 
since the movement of a simple body is simple, and the 
simple movements are finite, and every natural body must 
5 always have its proper motion. Now if ^ the infinite body is 
to be composed oi 2i finite number of kinds, then each of its 
parts must necessarily be infinite in quantity, that is to 
say, the water, fire, &c., which compose it. But this is 
impossible, because, as v/e have already shown, infinite 
weight and lightness do not exist. Moreover it would be 
necessary also that their places should be infinite in extent. 

10 so that the movements too of all these bodies would be in- 
finite. But this is not possible, if we are to hold to the 
truth of our original presuppositions and to the view that 
neither that which moves downward, nor, by the same 
reasoning, that which moves upward, can prolong its miove- 
ment to infinity. For it is true in regard to quality, 
quantity, and place alike that any process of change is 

15 impossible which can have no end. I mean that if it is im- 
possible for a thing to have come to be white, or a cubit 
long, or in Egypt, it is also impossible for it to be in process 
of coming to be any of these. It is thus impossible for a 
thing to be moving to a place'at which in its motion it can 
never by any possibility arrive. Again, suppose the body 
to exist in dispersion, it may be maintained none the less 
that the total of all these scattered particles, say, of fire, is 

20 infinite.^ But body we saw to be that which has exten- 
sion every way. How can there be several dissimilar ele- 
ments, each infinite? Each would have to be infinitely 
extended every way. 

It is no more conceivable, again^ that the infinite should 
exist as a whole of similar parts. For, in the first place, 

^ Reading dyi with FIIMJ. 

'^ *As Anaxagoras seems to have supposed' (Simpl.). 



BOOK I. 7 274I 

there is no other (straight) movement beyond those men- 
tioned : we must therefore give it one of them. And if so, 
we shall have to admit either infinite weight or infinite 25 
lightness. Nor, secondly, could the body whose movement 
is circular be infinite, since it is impossible for the infinite 
to move in a circle. This, indeed, would be as good as 
saying that the heavens are infinite, which we have shown 
to be impossible. 

Moreover, in general, it is impossible that the infinite 30 
should move at all. If it did, it would move either natur- 
ally or by constraint : and if by constraint, it possesses also 
a natural motion, that is to say, there is another place, 
infinite Hke itself, to which it will move. But that is 
impossible.^ 

That in general it is impossible for the infinite to be acted 
upon by the finite or to act upon it may be shown as 
follows. 

(i. The infinite cannot be acted upon by the finite^ Let 275' 
A be an infinite, B a finite, C the time of a given movement 
produced by one in the other. Suppose, then, that A was 
heated, or impelled, or modified in any way, or caused to 
undergo any sort of movement whatever, by B in the time 
C. Let D be less than B ; and, assuming that a lesser 
agent moves a lesser patient in an equal time, call the quan- 5 
tity thus modified by Z>, E. Then, as D is to B, so is E 
to some finite quantum. We assume that the alteration of 
equal by equal takes equal time, and the alteration of less 
by less or of greater by greater takes the same time, if the 
quantity of the patient is such as to keep the proportion 
which obtains between the agents, greater and less. If so, 10 
no movement can be caused in the infinite ^ by any finite 
agent in any time whatever. For a less agent will produce 
that movement in a less patient in an equal time, and the 
proportionate equivalent of that patient will be a finite 

^ Because an infinite place cannot exclude, or be 'other' than, any 
finite place. This argument applies to natural as well as unnatural 
movement : for a body moves naturally in the effort to reach its place. 
— Read touos aXXos 'io-os with EL, confirmed by Simplicius [tottos 'laos 
aXkos, 239, 24). 

^ Read Kiut]6r](r€Tai with Simplicius and all MSS. except E. 



275* DE CAELO 

quantity, since no proportion holds between finite and 
infinite. 

{2. The infinite cannot act tipon the finite^ Nor, again, can 

15 the infinite produce a movement in the finite in any time 
whatever. Let A be an infinite, B'^ a finite, C the time of 
action. In the time C, D will produce that motion in a 
patient less than B^ say F. Then take E^ bearing the same 
proportion to D as the whole BF bjsars to F. E will pro- 
duce the motion in BF in the time C. Thus the finite and 

20 the infinite effect the same alteration in equal times. But 
this is impossible ; for the assumption is that the greater 
effects it in a shorter time. It will be the same with any 
time that can be taken, so that there will be no time in which 
the infinite can effect this movement. And, as to infinite time, 
in that nothing can move another or be moved by it. For 
such time has no limit, while the action and reaction have. 
(3. There is no interaction between infinites.) Nor can 

25 infinite be acted upon in any way by infinite. Let A and B 
be infinites, CD being the time of the action of A upon B. 
Now the whole B was modified in a certain time, and the 
part of this infinite, E, cannot be so modified in the same 
time, since we assume that a less quantity makes the move- 
ment in a less time. Let E then, when acted upon by A^ 

30 complete the movement in the time D. Then, as D is to 
CD^ so is E to some finite part of B. This part will neces- 
sarily be moved by A in the time CD. For we suppose 
that the same agent produces a given effect on a greater 
275^ and a smaller mass in longer and shorter times, the times 
and masses varying proportionately. There is thus no 
finite time in which infinites can move one another. Is 
their time then infinite? No, for infinite time has no end, 
but the movement communicated has. 

5 If therefore every perceptible body possesses the power 
of acting or of being acted upon, or both of these, it is im- 
possible that an infinite body should be perceptible. All 
bodies, however, that occupy place are perceptible. There 
is therefore no infinite body beyond the heaven. Nor again 
is there anything of limited extent beyond it. And so 

* Called BF a few lines below. 



BOOK I. 7 275^ 

beyond the heaven there is no body at all. For if you 
suppose it an object of intelligence, it will be in a place — 10 
since place is what ' within ' and ' beyond ' denote — and 
therefore an object of perception. But nothing that is not 
in a place is perceptible.^ 

The question may also be examined in the light of more 
general considerations as follows. The infinite, considered 
as a whole of similar parts, cannot, on the one hand, move 
in a circle. For there is no centre of the infinite, and that 
which moves in a circle moves about the centre. Nor again 15 
can the infinite move in a straight line. For there would 
have to be another place infinite like itself to be the goal of 
its natural movement and another, equally great, for the 
goal of its unnatural movement. Moreover, whether its 
rectilinear movement is natural or constrained, in either 
case the force which causes its motion will have to be 20 
infinite. For infinite force is force of an infinite body, and 
of an infinite body the force is infinite. So the motive body 
also will be infinite. (The proof of this is given in our dis- 
cussion of movement,^ where it is shown that no finite thing 
possesses infinite power, and no infinite thing finite power.) 
If then that which moves naturally can also move unnatur- 
ally, there will be two infinites, one which causes, and 25 
another which exhibits the latter motion. Again, what is 
it that moves the infinite ? If it moves itself, it must be 
animate. But how can it possibly be conceived as an 
infinite animal? And if there is something else that moves 
it, there will be two infinites, that which moves and that 
which is moved, differing in their form and power.^ 

■^ These sentences are rather disjointed, and read more like rough 
notes than a finished argument. The final remark seems inconsequent. 
We should expect : ' but what is not perceptible cannot occupy 
a place ' ; so that the hypothesis that the body beyond the heaven 
is votjTov contradicts itself. The main point, however, is that all these 
connected attributes are inapplicable to an object of intelligence like 
the Platonic el8os. 

2 Pkys. VIII. X. 

^ The last argument (from ' Again, what is it ... ') is not a mere 
repetition of the preceding. The preceding sentence shows that an 
infinite disturbing force is needed to account for any unnatural move- 
ment of an infinite body. Finally, it is suggested that even the natural 
or normal movement of such a body would presuppose an independent 
infinite force. Again, the foregoing argument applied only to rectilinear 



275^ DE CAELO 

30 If the whole is not continuous, but exists, as Democritus 
and Leucippus think, in the form of parts separated by 
void, there must necessarily be one movement of all the 
multitude. They are distinguished, we are told, from one 
2^5^ another by their figures ; but their nature is one, like many 
pieces of gold separated from one another. But each piece 
must, as we assert, have the same motion. For a single 
clod moves to the same place as the whole mass of earth, 
and a spark to the same place as the whole mass of fire. 
So that if it be weight that all possess, no body is, strictly 
5 speaking, light ; and if lightness ^ be universal, none is 
heavy. Moreover, whatever possesses weight or lightness 
will have its place either at one of the extremes or in the 
middle region. But this is impossible while the world is 
conceived as infinite. And, generally, that which has no 
centre or extreme limits no up or down, gives the bodies no 
TO place for their motion ; and without that movement is 
impossible.. A thing must move either naturally or un- 
naturally, and the two movements are determined by the 
proper and alien places. Again, a place in which a thing 
rests or to which it moves unnaturally, must be the natural 
15 place for some other body, as experience shows. Neces- 
sarily, therefore, not everything possesses weight or lightness, 
but some things do and some do not. From these argu- 
ments then it is clear that the body of the universe is not 
infinite. 

We must now proceed to explain why there cannot be 8 
more than one heaven — the further question mentioned 
above. ^ For it may be thought that we have not proved 
20 universally of bodies that none whatever can exist outside 

movement, since unnatural circular movement has been shown to be 
impossible : but the last argument would apply equally to circular 
movement. The remark ' if it moves itself, it must be animate ' 
implies that it is incorrect to think of the natural movement of the 
elements as self-movement. It is only movement uninfluenced by 
any sublunary body. That self-movement is impossible Aristotle has 
already shown in J'hys. VII. 

' Prantl misprints fi for ft. 

^ In 1. 18 Prantl's Xeyofxeu seems to be a misprint for Xeyco/Kv. — 
* Heaven' here stands of course for world {ovpavos = Koa/jLOi:), — The 
reference is to c. vi (274^24). 



BOOK I. 8 276^ 

our universe, and that our argument applied only to those 
of indeterminate extent. 

Now all things rest and move naturally and by con- 
straint. A thing moves naturally to a place in which it 
rests without constraint, and rests naturally in a place to 
which it moves without constraint.' On the other hand, 25 
a thing moves by constraint to a place in which it rests by 
constraint, and rests by constraint in a place to which it 
moves by constraint. Further, if a given movement is due 
to constraint, its contrary is natural. If, then, it is by con- 
straint that earth moves from a certain place to the centre 
here^ its movement from here to there will be natural, and 
if earth from there rests here without constraint, its move- 
ment hither will be natural. And the natural movement 30 
in each case is one.^ Further, these worlds, being similar in 
nature to ours, must all be composed of the same bodies as 
it. Moreover each of the bodies, fire, I mean, and earth 
and their intermediates, must have the same power as in 276^ 
our world. For if these names are used equivocally, if the 
identity of name does not rest upon an identity of form in 
those elements and ours, then the whole to which they 
belong can only be called a world by equivocation. Clearly, 
then, one of the bodies will move naturally away from the 5 
centre and another towards the centre, since fire must be 
identical with fire, earth with earth, and so on, as the frag- 
ments of each are identical in this world. That this must 
be the case is evident from the principles laid down in our 
discussion of the movements ; ^ for these are limited in 
number, and the distinction of the elements depends upon 
the distinction of the movements. Therefore, since the 10 
movements are the same, the elements must also be the 
same everywhere. The particles of earth, then, in another 
world move naturally also to our centre and its fire to our 
circumference. This, however, is impossible, since, if it 
were true, earth must, in its own world, move upwards, and 15 
fire to the centre ; in the same way the earth of our world 

^ Reading fxla d' rj with EF^M Alex. The yap of the other MSS. 
and Simpl. is misleading and suggests an argument where there is 
none. The principle is simply stated for future use. 

^ Above, cc. ii-iv. 



276^ DE CAELO 

must move naturally away from the centre when it moves 
towards the centre of another universe.^ This follows from 
the supposed juxtaposition of the worlds. For either we 
must refuse to admit the identical nature of the simple 

20 bodies in the various universes, or, admitting this, we must 
make the centre and the extremity one as suggested. This 
being so, it follows that there cannot be more worlds than 
one.^ 

To postulate a difference of nature in the simple bodies 
according as they are more or less distant from their proper 
places is unreasonable. For what difference can it make 
whether we say that a thing is this distance away or that ? 

25 One would have to suppose a difference proportionate to 
the distance and increasing with it, but the form is in fact 
the same. Moreover, the bodies must have some movement, 
since the fact that they move is quite evident.^ Are we to 
say then that all their movements, even those which are 
mutually contrary, are due to constraint ? No, for a body 
which has no natural movement at all cannot be moved by 

30 constraint. If then the bodies have a natural movement, 

^ In 1. 17 the comma which Prantl places after (pvaiv should be 
placed instead after jxicrov. It is needed in this place in order to show 
that the following clause {hia to . . . a\\r]Xovs) is explanatory of the 

dvdyKr] of 1. 1 4, nOt oi (pepeadaL in 1. 1 6. 

^ If there is one centre and one extremity, there is only one heaven 
or world. (Read tovtov S' ovtos, ddvvaTou ktX. Prantl's aTonov is 
found only in F and J, and in both it is preceded by tov, which shows 
that it is an adscript intended to explain the meaning of tovtov.) — The 
argument of the chapter down to this point is a single reductio ad 
absiirdtwi. Simplicius tries unsuccessfully to interpret it as a series 
of reductions. The remainder of the chapter reasserts the conclusion 
here drawn by closing up various pathways of escape. In truth there 
is only one way of escape, as Aristotle here says, viz. to deny the 
identity of the fire and earth in the other worlds with that in our own ; 
but the contention takes a variety of forms — (i) 'distance makes 
a difference'; (2) 'they have no movement, or only move by con- 
straint' ; (3) ' the goal of their movement is only the same in kind djs, 
that of the corresponding elements here'. These suggestions are 
refuted in what follows. 

^ Throughout this paragraph when Aristotle speaks of ' the bodies ' 
he is thinking of the fire, earth, &c., supposed to constitute another 
KooTfxos. He is not proving over again the proposition that the four 
elements have each a natural motion, but considering what would be 
their motion in another world existing beside our own. The empirical 
evidence of movement here appealed to must be that of the fire and 
earth of this world ; but a thing that did not move would not be 
a body at all. 



BOOK I. 8 276^ 

the movement of the particular instances of each form must 
necessarily have for goal a place numerically one, i. e. a 
particular centre or a particular extremity. If it be sug- 
gested that the goal in each case is one in form but 
numerically more than one, on the analogy of particulars 277^ 
which are many though each undifferentiated in form, we 
reply that the variety of goal cannot be limited to this 
portion or that but must extend to all alike.^ For all are 
equally undifferentiated in form, but any one is different 
numerically from any other. What I mean is this : if the 5 
portions in this world behave similarly both to one another 
and to those in another world, then the portion which is 
taken hence will not behave differently either from the 
portions in another world or from those in the same world, 
but similarly to them, since in form no portion differs from 
another. The result is that we must either abandon our 
present assumptions or assert that the centre and the 10 
extremity are each numerically one. But this being so^, the 
heaven, by the same evidence and the same necessary 
inferences, must be one only and no more. 

A consideration of the other kinds of movement also 
makes it plain that there is some point to which earth and 
fire move naturally. For in general that which is moved 
changes from something into something, the starting- 15 
point and the goal being different in form, and always 
it is a finite change.^ For instance, to recover health 
is to change from disease to health, to increase is to 
change from smallness to greatness. Locomotion must be 
similar: for it also has its goal and starting-point — and 
therefore the starting-point and the goal of the natural 
movement must differ in form — ^just as the movement of 
coming to health does not take any direction which chance 20 

^ Read tm ixev tw S' oi) with FLJ Simpl. The meaning is that since 
none but a ' numerical ' difference can be postulated between the 
portions (e. g. of earth) in this world and those in 'another, and since 
a difference of goal can only be justified by a difference in the body, 
we should have to suppose a distinct goal for every single portion of 
earth ; which is absurd. 

^ A full-stop, rather than a comma, is needed after fxerajSoXr] in 1. 16. 
Three principles are laid down and all are illustrated in the case of 
locomotion. But the instances of health and increase are used only 
to illustrate the first. 



277^ DE CAELO 

or the wishes of the mover may select.^ Thus, too, fire and 
earth move not to infinity but to opposite points ; and since 
the opposition in place is between above and below, these 
will be the limits of their movement.^ (Even in circular 
movement there is a sort of opposition between the ends of 
the diameter, though the movement as a whole has no 
25 contrary : so that here too the movement has in a sense an 
opposed and finite goal.) There must therefore be some 
end to locomotion : it cannot continue to infinity. 

This conclusion that local movement is not continued to 
infinity is corroborated by the fact that earth moves more 
quickly the nearer it is to the centre, and fire the nearer it 
30 is to the upper place. But if movement were infinite speed 
would be infinite also ; and if speed then weight and light- 
ness. For as superior speed in downward movement 
implies superior weight, so infinite increase of weight neces- 
sitates infinite increase of speed.^ 
277^ Further, it is not the action of another body that makes 
one of these bodies move up and the other dowm ; nor is it 
constraint, like the ' extrusion ' of some writers.^ For in 
that case the larger the mass of fire or earth the slower 
would be the upward or downward movement ; but the fact 

^ 11. 18-19, the full-stop after ttoI should be deleted, and the words 
del (ipa . . . (pepfadai should be marked as a parenthesis. Locomotion, 
like healing, has a determinate direction, and that involves a difference 
of form between its two terms. 

'^ The remarks which follow concerning circular motion are a kind 
of footnote and would be best marked as a parenthesis. 

^ In 1. 29 it is tempting to read et d' els aneipov rjv for el 5' aireipov rjv, 
but no evidence of such a reading survives. The sense of the para- 
graph is plain. We observe an increase of speed in a falling body as 
it approaches the earth. The explanation, on our view, is the proximity 
of the goal. But if there is no goal, the movement, and with it the 
increase of speed, is capable of continuing to infinity. But infinite 
speed means infinite weight, which has already (c. vi) been proved 
impossible. The Greek of the last sentence is puzzling and may be 
corrupt. Accepting the text of Bckker and Prantl, we must translate 
as follows : 'as that which by reason of speed is lower than another 
body would be presumed speedy by reason of weight, so if there were 
infinite increase of weight there would also be infinite increase of 
speed.' (The alteration of an accent is required : (iapei for ^apel in 
1. 32.) The sentence is clumsy, but it gives the required sense. 
Simpliciiis seems to have interpreted the passage as above. In 1. 31 
(Ttpov is found in V alone, all the other MSS. giving erepov ; but 
erepov must be right. 

* The atomists, Leucippus and Democritus. 



BOOK I. 8 277^ 

is the reverse : the greater the mass of fire or earth the 
quicker always is its movement towards its own place. 5 
Again, the speed of the movement would not increase 
towards the end if it were due to constraint or extrusion ; 
for a constrained movement always diminishes in speed as 
the source of constraint becomes more distant, and a body 
moves without constraint to the place whence it was moved 
by constraint. 

A consideration of these points, then, gives adequate 
assurance of the truth of our contentions. The same could 
also be shown with the aid of the discussions which fall 10 
under First Philosophy,^ as w^ell as from the nature of the 
circular movement, which must be eternal both here and in 
the other worlds. It is plain, too, from the following con- 
siderations that the universe must be one. 

The bodily elements are three, and therefore the places of 
the elements will be three also ; the place, first, of the body 15 
which sinks to the bottom, namely the region about the 
centre ; the place, secondly, of the revolving body, namely 
the outermost place, and thirdly, the intermediate place, 
belonging to the intermediate body. Here in this third 
place \vill be the body which rises to the surface ; since, if 
not here, it will be elsewhere, and it cannot be elsewhere : 
for we have two bodies, one weightless, one endowed with 
weight, and below is the place of the body endowed with 20 
weight, since the region about the centre has been given to 
the heavy body. And its position cannot be unnatural to 
it, for it would have to be natural to something else, and 
there is nothing else. It must then occupy the intermediate 
place. What distinctions there are within the intermediate 
itself we will explain later on. 

We have now said enough to make plain the character and 
number of the bodily elements, the place of each, and fur- 
ther, in general, how many in number the various places are. 25 

9 We must show not only that the heaven is one,^ but 
also that more than one heaven is impossible, and, further, 

^ i.e. r^Ietaphysics. Cf. Met. A. 8. 

^ Prantl misprints ets- for],etf. For ovpaucs read 6 nipavos with M. 
J, like EHL,_^omits the word olpavos altogether. 



277^ DE CAELO 

that, as exempt from decay and generation, the heaven 
is eternal. We may begin by raising a difficulty. From 

3c one point of view it might seem impossible that the 
heaven should be one and unique,^ since in all formations 
and products whether of nature or of art we can distinguish 

- the shape in itself and the shape in combination with matter. 
278^ For instance the form of the sphere is one thing and the 
gold or bronze sphere another ; the shape of the circle 
again is one thing, the bronze or wooden circle another. 
For when we state the essential nature of the sphere or 
circle we do not include in the formula gold or bronze, 
5 because they do not belong to the essence, but if we 
are speaking of the copper or gold sphere we do in- 
clude them. We still make the distinction even if we 
cannot conceive or apprehend any other example beside 
the particular thing. This may, of course, sometimes be 
the case : it might be, for instance, that only one circle 
could be found ; yet none the less the difference will 
remain between the being of circle and of this particular 
circle, the one being form, the other form in matter, 

10 i. e. a particular thing. Now since the universe is per- 
ceptible it must be regarded as a particular ; for every- 
thing that is perceptible subsists, as we know, in matter. 
But if it is a particular, there will be a distinction between 
the being of ' this universe ' and of ' universe ' unqualified. 
There is a difference, then, between 'this universe' and 
simple 'universe'; the second is form and shape, the first 

15 form in combination with matter ; and any shape or form 
has, or may have, more than one particular instance. 

On the supposition of Forms such as some assert, this 
must be the case, and equally on the view that no such 
entity has a separate existence. For in every case in 
which the essence is in matter it is a fact of observation 
that the particulars of like form are several or infinite in 

20 number. Hence there either are,, or may be, more heavens 

^ More correctly : that the heaven should be 7iecessarily one and 
unique. The argument here set out only attempts to prove the 
possibility of more than one world, and Aristotle replies by proving 
the impossibility of more than one. Alexander (cited by Simpl.) 
points out this defect in the statement. 



BOOK I. 9 278^ 

than one.^ On these grounds, then, it might be inferred 
either that there are or that there might be several heavens. 
We must, however, return and ask how much of this argu- 
ment is correct and how much not. 

Now it is quite right to say that the formula of the 
shape apart from the matter must be different from that 
of the shape in the matter, and we may allow this to be 25 
true. We are not, however, therefore compelled to assert 
a plurality of worlds. Such a plurality is in fact impossible 
if this world contains the entirety of matter, as in fact 
it does. But perhaps our contention can be made clearer 
in this way. Suppose ' aquilinity ' to be curvature in the 
nose or flesh, and flesh to be the matter of aquilinity. 30 
Suppose, further, that all flesh came together into a single 
whole of flesh endowed with this aquiline quality. Then 
neither would there be, nor could there arise, any other 
thing that was aquiline. Similarly, suppose flesh and bones 
to be the matter of man, and suppose a man to be created 
of all flesh and all bones in indissoluble union. The 35 
possibility of another man would be removed. Whatever 
case you took it would be the same. The general rule 278^ 
is this : a thing whose essence resides in a substratum 
of matter can never come into being in the absence of 
all matter.^ Now the universe is certainly a particular 
and a material thing : if however it is composed not of 
a part but of the whole of matter, then though the being 5 
of ' universe ' and of ' this universe ' are still distinct, yet 
there is no other universe, and no possibility of others 
being made, because all the matter is already included 
in this. It remains, then, only to prove that it is composed 
of all natural perceptible body. 

First, however, we must explain what we mean by ' heaven ' 10 
and in how many senses we use the word, in order to make 
clearer the object of our inquiry, {a) In one sense, then, we call 

^ The 01 before ovpaioi is attributed only to E, and to it ' dubio '. 
J has it. But the article does not seem to be required here. In 
corresponding passages in this chapter it is omitted. 

^ Read nvo? vXt]^. The omission of tlvus in E must be a mere slip. 
All the other MSS., as well as Simpl., have nuis v\r]s, and E is full of 
small omissions. 



278^ DE CAELO 

' heaven' the substance of the extreme drcumference of the 
whole, or that natural body whose place is at the extreme 
circumference. We recognize habitually a special right to 

15 the name 'heaven' in the extremity or upper region, which 
we take to be the seat of all that is divine.^ {b) In another 
sense, we use this name for the body continuous with the 
extreme circumference, which contains the moon, the sun, 
and some of the stars ; these we say are ' in the heaven '. 
(c) In yet another sense we give the name to all body 

20 included within the extreme circumference, since we habi- 
tually call the whole or totality 'the heaven '. The word, 
then, is used in three senses. 

Now the whole included within the extreme circumference 
must be composed of ^// physical and sensible body, because 
there neither is, nor can come into being, any body outside 

25 the heaven. For if there is a natural body outside the 
extreme circumference it must be either a simple or a com- 
posite body, and its position must be either natural or 
unnatural. But it cannot be any of the simple bodies. 
For, first, it has been shown ^ that that which moves in a circle 

30 cannot change its place. And, secondly, it cannot be that 
which moves from the centre or that which lies lowest. 
Naturally they could not be there, since their proper places 
are elsewhere ; and if these are there unnaturally^ the 
exterior place will be natural to some other body, since 
a place which is unnatural to one body must be natural 
to another : but we saw that there is no other body besides 

35 these. ^ Then it is not possible that any simple body should 
279^ be outside the heaven. But, if no simple body, neither can 
any mixed body be there : for the presence of the simple 
body is involved in the presence of the mixture. Further 
neither can any body come into that place : for it will do so 
either naturally or unnaturally, and will be either simple 
5 or composite ; so that the same argument will apply, since 
it makes no difference whether the question is * does A 

' Place a full-stop after (fiafx^v. In the next line o-wex^s should be 

2 Read to nev yap. The /ue'i/ is wanted, and is omitted by E alone. 
The reference is to cc. ii and iii above. 
' c. ii above. 



BOOK I. 9 279^ 

exist ? ' or * could A come to exist ? ' From our arguments 
then it is evident not only that there is not, but also that there 
could never come to be, any bodily mass whatever outside 
the circumference. The world as a whole, therefore, includes 
all its appropriate matter, which is, as we saw, natural 
perceptible body. So that neither are there now, nor have 
there ever been, nor can there ever be formed more heavens 10 
than one, but this heaven of ours is one and unique and 
complete. 

It is therefore evident that there is also no place or void 
or time outside the heaven. For in every place body can 
be present ; and void is said to be that in which the presence 
of body, though not actual, is possible ; and time is the 15 
number of movement. But in the absence of natural body 
there is no movement, and outside the heaven, as we have 
shown, body neither exists nor can come to exist. It is 
clear then that there is neither place, nor void, nor time, 
outside the heaven. Hence whatever is there, is of such 
a nature as not to occupy any place, nor does time age it ; 
nor is there any change in any of the things which lie beyond 20 
the outermost motion ; they continue through their entire 
duration unalterable and unmodified, living the best and 
most self-sufficient of lives. As a matter of fact, this word 
' duration ' possessed a divine significance for the ancients, 
for the fulfilment which includes the period of life of any 
creature, outside of which no natural development can fall, 
has been called its duration. On the same principle the 25 
fulfilment of the whole heaven, the fulfilment which includes 
all time and infinity, is ' duration ' — a name based upon the 
fact that it is always'^ — duration immortal and divine. 
From it derive the being and life which other things, 
some more or less articulately but others feebly, enjoy. 30 
So, too, in its discussions concerning the divine, popular 
philosophy^ often propounds the view that whatever is 

^ i.e. ala>v is derived from ae\ Siv. 

^ Aristotle refers apparently under this name to elementary hand- 
books of philosophy current among his audience. It is usual to 
identify them with the e'lcorepiKoi Xoyot, as Simpl. does in his com- 
mentary on this passage. See Bonitz, Ind. Ar., s. v. 'ApiaroreXf;?, 
105*27. 

645.20 D 



279* DE CAELO 

divine, whatever is primary and supreme, is necessarily 
unchangeable. This fact confirms what we have said. 
For there is nothing else stronger than it to move it — 
35 since that would mean more divine — and it has no defect 
279^ and lacks none of its proper excellences. Its unceasing 
movement, then, is also reasonable, since everything ceases 
to move when it comes to its proper place, but the body 
whose path is the circle has one and the same place for 
starting-point and goal. 

Having established these distinctions, we may now pro- 10 
5 ceed to the question whether the heaven is ungenerated 
or generated, indestructible or destructible. Let us start 
with a review of the theories of other thinkers ; for the 
proofs of a theory are difficulties for the contrary theory.^ 
Besides, those who have first heard the pleas of our 
adversaries will be more likely to credit the assertions 
10 which we are going to make. We shall be less open 
to the charge of procuring judgement by default. To 
give a satisfactory decision as to the truth it is necessary 
to be rather an arbitrator than a party to the dispute. 

That the world was generated all are agreed, but, genera- 
tion over, some say that it is eternal, others say that it is 
destructible like any other natural formation.^ Others 
15 again, with Empedocles of Acragas and Heraclitus of 
Ephesus, believe that there is alternation in the destructive 
process, which takes now this direction, now that, and 
continues without end.^ 

^ Prantl misprints tvv evavricov for rcbv evavrlcov in 1. 6. 

^ The former view, according to Alexander (a^. Simpl.), is that of 
Orpheus (i. e. of Orphic cosmogony), Hesiod, and Plato, while the 
latter is that of Democritus and his school. 

^ Cf. Burnet, E.G.P.^ p. 157 (§ yy). Heraclitus and Empedocles 
are agreed in believing in periodic changes in the constitution of our 
world as a whole. For both, the world exists, as it were, in a succession 
of lives (below, 280*14); and the view is a kind of compromise 
between that which regards it as eternal and that which gives it 
a single life ended by annihilation. The phrase 'alternation in the 
destructive process' is somewhat inaccurate, since the alternation 
may be described as between generation and destruction (Empedocles' 
Love and Strife, Stoic dinKocrfiijais and (KTrvpaiaLs). But it is intelligible. 
Aristotle is here classing the theory for convenience with those that 
hold to a destructible world, and the antithesis is between destruction 
aTrXaJy and destruction with alternation. Later he explains that this 



BOOK I. lo 279^ 

Now to assert that it was generated and yet is eternal is 
to assert the impossible ; for we cannot reasonably attribute 
to anything any characteristics but those which observation 
detects in many or all instances. But in this case the facts 20 
point the other way : generated things are seen always to 
be destroyed. Further, a thing whose present state had no 
beginning and which could not have been other than it was at 
any previous moment throughout its entire duration, cannot 
possibly be changed.^ For there will have to be some cause 
of change, and if this had been present earlier it .would have 
made possible another condition of that to which any other 
condition was impossible. Suppose that the world was formed 25 
out of elements which were formerly otherwise conditioned 
than as they are now. Then (i) if their condition was always 
so and could not have been otherwise, the world could never 
have come into being.^ And (2) if the world did come into 
being, then, clearly, their condition must have been capable 
of change and not eternal : after combination therefore they 
will be dispersed, just as in the past after dispersion they 
came into combination, and this process either has been, 
or could have been, indefinitely repeated. But if this is so, 30 
the world cannot be indestructible, and it does not matter 
whether the change of condition has actually occurred or 
remains a possibility. 

Some of those who hold that the world, though in- 
destructible, was yet generated, try to support their case 
by a parallel which is illusory.^ They say that in their 
statements about its generation they are doing what 
geometricians do when they construct their figures, not 35 
implying that the universe really had a beginning, but 

alternation is not (f)dopd at all. Burnet in his first edition proposed to 
excise cpdeLpofxevov, but the suggestion is now tacitly retracted. In 
his later editions Burnet wrongly states that what is here in 
question is the eternity of the first heaven. That has already been 
proved in c. iii, and the first heaven would not be referred to as 
6 Koafxos. 

^ A comma is required after alcova in 1. 22, unless the comma after 
€x^i-v in the preceding line is deleted. 

"^ The close coordination of el /xeV (in 1. 25) with el 8e (in 1. 26) 
demands a comma, rather than a full-stop, after iyevero. 

^ Simpl. refers the following argument to Xenocrates and the 
Platonists. 

D 2 



28o^ DE CAELO 

280^ for didactic reasons facilitating understanding by exhibiting 
the object, like the figure, as in course of formation. The 
two cases, as we said, are not parallel ; for, in the construc- 
tion of the figure, when the various steps are completed 
the required figure forthwith results; but in these other 
demonstrations what results is not that which was required.^ 
5 Indeed it cannot be so ; for antecedent and consequent, as 
assumed, are in contradiction. The ordered, it is said,'^ 
arose out of the unordered ; and the same thing cannot 
be at the same time both ordered and unordered ; there 
must be a process and a lapse of time separating the two 

10 states. In the figure, on the other hand, there is no 
temporal separation.^ It is clear then that the universe 
cannot be at once eternal and generated. 

To say that the universe alternately combines and dissolves 
is no more paradoxical than to make it eternal but vary- 
ing in shape. It is as if one were to think that there was now 

15 destruction and now existence when from a child a man is 
generated, and from a man a child. For it is clear that when 
the elements come together the result is not a chance system 
and combination, but the very same as before — especially 
on the view of those who hold this theory, since they say 
that the contrary is the cause of each state. ^ So that if 

20 the totality of body, which is a continuum, is now in this 
order or disposition and now in that, and if the combination 
of the whole is a world or heaven, then it will not be the 
world that comes into being and is destroyed, but only 
its dispositions. 

If the world is believed to be one, it is impossible to 

^ i.e. the geometricians can truly write O. E.F. at the end of their 
construction, but these cosmogonists cannot. The figure, or world, 
constructed should be ' the same ' {to avro) as that demanded in the 
vnodscTLs. 

2 Cp. Plato, Ihnaeics 30 A. 

^ The construction of the cosmogonist cannot be a mere didactic 
device like that of the geometrician ; for the attributes successively 
assumed in the construction of the world cannot exist simultaneously 
as those assumed by the geometrician do. 

^ Here Aristotle clearly refers to Kmpedocles, rather than to 
Heraclitus. The two causes of Empedocles are Love and Strife 
(^iXi'a and i/fiAcoy), and since these are two it follows, Aristotle argues, 
that the world would merely oscillate between two arrangements or 
dispositions. 



BOOK I. lo 280^ 

suppose that it should be, as a whole, first generated and 
then destroyed, never to reappear ; since before it came 
into being there was always present the combination prior 25 
to it, and that, we hold, could never change if it was never 
generated. If, on the other hand, the worlds are infinite 
in number the view is more plausible. But whether this 
is, or is not, impossible will be clear from what follows. 
For there are some who think it possible both for the 
ungenerated to be destroyed and for the generated to 30 
persist undestroyed."^ (This is held in the Timaeiis'^ 
Avhere Plato says that the heaven, though it was generated, 
will none the less exist to eternity.) So far as the heaven 
is concerned we have answered this view with arguments 
appropriate to the nature of the heaven : on the general 
question we shall attain clearness when we examine the 
matter universally.^ 

II We must first distinguish the senses in which we use the 280^ 
words 'ungenerated' and 'generated', 'destructible' and 
' indestructible '.^ These have many meanings, and though 

^ In 1. 29 Prantl misprints k\}.'i for Ka'u 

^ A colon instead of a full-stop is needed after TLfialco. The reference 
is to Plato, Timaeus 31. Plato is quoted as authority for the in- 
destructible-generated not for the ungenerated-destructible, as the 
context shows. 

^ The general question is the mutual relations of the terms 'generated', 
■ ungenerated '. '' destructible ', ' indestructible ', which have so far been 
considered only in their application to the heaven. The terms are 
discussed universally, i.e. apart from any special application, in 
cc. xi and xii. The combination attributed to Plato is refuted at the 
end of that discussion (283^ i ff.). Simplicius found the argument of 
the last paragraph of this chapter (11. 23 If.) somewhat obscure. It 
deals, provisionally and subject to further investigation, with the view- 
that the world is subject both to generation and to destruction in the 
sense in which the man Socrates is. Simpl. is probably right in 
supposing that under this head Aristotle is thinking of the atomists. 
Their infinite worlds were successive, if also co-existent. Aristotle 
here argues that if that out of which the world was formed had the 
capacity to give birth to a world, then that into which the world is 
destroyed will have the same capacity. Thus the theoiy of world- 
annihilation is dismissed as absurd, while the infinite succession of 
destructible worlds is left open. But the refutation even of the first 
of these views, and therefore a fo7-tiori of the second, cannot be 
regarded as complete until the whole problem of generation and 
destruction has been examined. 

* It is unfortunate that 'generated' and 'destructible' are not 
similar grammatical forms as the Greek y^v^ro^ and (fidaprof are. 
But from the analysis given by Aristotle it will be seen that in 
meaning the Greek verbal adjective tends to approximate to the past 



280^^ DE CAELO 

it may make no difference to the argument, yet some con- 
fusion of mind must result from treating as uniform in its 
5 use a word which has several distinct applications. The 
character which is the ground of the predication will 
always remain obscure. 

The word ' ungenerated ' then is used (a) in one sense 
whenever something now is which formerly was not, no 
process of becoming or change being involved. Such is the 
case, according to some, with contact and motion, since 
there is no process of coming to be in contact or in motion. 
(d) It is used in another sense, when something which is 

10 capable of coming to be, with or without process, does not 
exist ; such a thing is ungenerated in the sense that its 
generation is not a fact but a possibility, (c) It is also 
applied where there is general impossibility of any generation 
such that the thing now is which then was not. And ' im- 
possibility ' has two uses : first, where it is untrue to say 
that the thing can ever come into being, and secondly, 
where it cannot do so easily, quickly, or well. In the 

15 same way the word 'generated' is used, (a) first, where 
what formerly was not afterwards is, whether a process of 
becoming was or was not involved, so long as that which 
then was not, now is ; {d) secondly, of anything capable of 
existing, ' capable ' being defined with reference either to 
truth or to facility ; (c) thirdly, of anything to which the 
passage from not being to being belongs,^ whether already 
actual, if its existence is due to a past process of becoming, 

20 or not yet actual but only possible. The uses of the words 
' destructible ' and ' indestructible ' are similar. * Destruc- 
tible ' is applied (a) to that which formerly was and after- 
wards either is not or might not be, whether a period of 
being destroyed and changed intervenes or not ; '^ and (/;) 

participle, and therefore it is not worth while to insist on 'generable', 
' ungenerablc ' for yeurjTos, dyeuT]Tos. 

^ For eau T] yiveais read eav fj yepeais. (M has ^ 17, but all Other 
MSS. have rj.) The correction was suggested by Hayduck (Greifs- 
wald Gymnasium Program, 1871, p. 11). 

^ The evidence afforded by Simpl. and the MSS., together with the 
difficulty of establishing a precise correspondence between this defini- 
tion of <^6apT()V and the parallel uses of 'ungenerated' {b) and 
'generated' («), might lead one to doubt the soundness of the text 
at this point ; but it is guaranteed by Aristotle's own citation at 
281'' 27. 



BOOK I. II 280' 

sometimes we apply the word to that which a process of 
destruction may cause not to be ; and also (c) in a third 
sense, to that which is easily destructible, to the ' easily- 25 
destroyed ', so to speak.^ Of the indestructible the same 
account holds good. It is either (a) that which now is and 
now is not, without any process of destruction, like contact, 
which without being destroyed afterwards is not, though 
formerly it was ; or (d) that which is but might not be, or 
which will at some time not be, though it now is.^ For you 
exist now and so does the contact ; yet both are destructible, 30 
because a time will come when it will not be true of you 
that you exist, nor of these things that they are in contact. 
Thirdly (c) in its most proper use, it is that which is, but is 
incapable of any destruction such that the thing which now 
is later ceases to be or might cease to be ; or again, that 
which has not yet been destroyed, but in the future may 
cease to be.^ For indestructible is also used of that which 281^ 
is destroyed with difficulty.* 

^ Aristotle carelessly omits to mention the other and more exact 
kind of possibility. Cf. ' ungenerated ' (c) and 'generated' (d). 

^ The third ^ (in 1. 29) is not coordinate with the two which precede 
it (11. 26, 28), and it would be well to mark this by putting a colon 
instead of a comma after elaiv in 1. 28. Simplicius read rj /cat om in 
1. 29, and the addition of /cat would be an improvement. 

^ Omit the ovk inserted by Prantl before ivdexofiepov. The ov Be 
which Prantl's note attributes to Simplicius is found only in one 
inferior MS. and is not printed in Heiberg's text of the commentary. 
J also has no word between ecpdapfxhop and eV6exo'fiei/or, nor had 
Alexander. 

* Read Xeyerai yap for Xe-yerai ds, and place a colon instead of a full- 
stop before Xeyerai. This alteration is conjectural, but it is preferable 
to Hayduck's excision of 1) /cat . . . elvai (11. 33, 34), and without some 
alteration the Greek will not give a satisfactory sense. The account 
given of * indestructible ' is closely parallel to that given of ' un- 
generated ' above. Sense (a) of ' indestructible ' (11. 26-28) turns on 
the absence of process, like sense (a) of ' ungenerated ', even repeating 
the same instance, touch. In sense (^) (11. 28-31) 'indestructible' 
covers all that has not been destroyed, as 'ungenerated' in sense (d) 
covers what has not yet come into being : as ' ungenerated ' includes 
all possible existents which are now non-existent, so 'indestructible' 
includes all possible non-existents which are now existent. There 
remains the third and proper sense, viz. potentiality or possibility, 
subdivided in the case of ' ungenerated ', according to an ambiguity 
in the word possible, into (i) strict and final impossibility (tw fxr) 
a\r}des elvai elTrelv), (ii) popular or 'practical' impossibility (rw fxr) 
pahiws pr]5€ raxv v /caXcos). The third sense of ' indestructible ' is 
introduced by to 8e paXiara Kvpicos in I. 31, and its subdivision 
is effected by ^ /cat in 1. 33. The words before ^ /cat assert the final 



28i^ DE CAELO 

This being so, we must ask what we mean by * possible ' 
and ' impossible '. For in its most proper use the predicate 
' indestructible ' is given because it is impossible that the 
thing should be destroyed, i. e. exist at one time and not at 
5 another. And ^ ungenerated ' also involves impossibility 
when used for that which cannot be generated, in such 
fashion that; while formerly it was not, later it is. An in- 
stance is a commensurable diagonal. Now when we speak 
of a power ^ to move ^ or to lift weights, we refer always to 
the maximum. We speak, for instance, of a power to lift 
a hundred talents or walk a hundred stades — though 
a power to effect the maximum is also a power to effect any 

10 part of the maximum — since we feel obliged in defining the 
power to give the limit or maximum. A thing, then, which 
is capable of a certain amount as maximum must also be 
capable of that which lies within it. If, for example, a man 
can lift a hundred talents, he can also lift two, and if he can 
walk a hundred stades, he can also walk two. But the 

15 power is of the maximum, and a thing said, with reference 
to its maximum,^ to be incapable of so much is also in- 
capable of any greater amount. It is, for instance, clear 
that a person who carniot walk a thousand stades will also 
be unable to walk a thousand and one. This point need 
not trouble us, for we may take it as settled that what is, in 
the strict sense, possible is determined by a limiting maxi- 

20 mum. Now perhaps the objection might be raised that 

removal of the possibility of non-existence, and the following clause 
relaxes the requirement as popular use demands. Even if the possi- 
bility of destruction has not been finally removed, a thing may be 
called 'indestructible' in this sense if it has not been destroyed. 
''For (Af'yerat -yap) what is not easily destroyed is called indestructible.' 
By calling this the proper sense, whether in its stricter or more 
popular use, Aristotle must mean that the verbal adjective in -ro^ 
should not in precise speech be allowed to approximate, as it often 
does, to a past participle passive. (Simplicius's interpretation of this 
passage is quite inadmissible, but he was confused by faulty MSS.) 

^ 'Power' (dvpafiLs) must be taken throughout as the noun corre- 
sponding to the adjective ' possible ' {8vvut6v). 

^ The MSS. have KivijOPjvai crraSm (Karov ('to move a hundred 
stades 'j. The translation omits the reference to distance, which 
seems clearly out of place. The words o-raSm tKnroV, which occur 
more than once in the context, probably got their place in this clause 
through a copyist's mistake. 

•■ Frantl misprints vTrfp^aXtjv for vrrfp^oXrjv. 



BOOK I. II 281^ 

there is no necessity in this, since he who sees a stade need 25 
not see the smaller measures contained in it, while, on the 
contrary, he who can see a dot or hear a small sound will 
perceive what is greater. This, however, does not touch 
our argument. The maximum may be determined either 
in the power or in its object.^ The application of this is 
plain. Superior sight is sight of the smaller body, but 
superior speed is that of the greater body. 

12 Having established these distinctions we can now proceed 
to the sequel. If there are things capable both of being 
and of not being, there must be some definite maximum 
time of their being and not being ; a time, I mean^ during 30 
which continued existence is possible to them and a time 
during which continued non-existence is possible. And 
this is true in every category, whether the thing is, for ex- 
ample, ' man ', or ' white ', or ' three cubits long ', or whatever 
it may be. For if the time is not definite in quantity, but 
longer than any that can be suggested and shorter than 
none, then it will be possible for one and the same thing to 28f 
exist for infinite time and not to exist for another infinity. 
This, however, is impossible. 

Let us take our start from this point. The impossible 
and the false have not the same significance. One use of 
' impossible ' and ' possible ', and ' false ' and '' true ', is hypo- 5 
thetical. It is impossible, for instance, on a certain 
hypothesis that the triangle should have its angles equal to 
two right angles, and on another the diagonal is commen- 
surable. But there are also things possible and impossible, 
false and true, absolutely. Now it is one thing to be abso- 
lutely false, and another thing to be absolutely impossible. 
To say that you are standing when you are not standing is 
to assert a falsehood, but not an impossibility. Similarly 10 

^ i.e. sometimes the maximum is an actual maximum (determined 
'in the object', eVt rov Trpd-y^arof), e. g. in the case of weight-hfting, 
where the largest weight lifted serves to define the power ; sometimes 
it is an actual minimum, determined as maximum ' in the power ' 1 fVl 
Tr)? 8vvdnea)s), e.g. in the case of vision, where the smallest object seen 
serves to define the capacity. Cf. the distinction between the fiiaou 
Tov Trpdyixaros (or Kara to Trpdyfui) and the piaov irpbs Tjfins in Et/l. AIl. 
1 1 06» 26 ff. 



28i^ DE CARLO 

to say that a man who is playing the harp, but not singing, 
is singing, is to say what is false but not impossible. To 
say, however, that you are at once standing and sitting, or 
that the diagonal is commensurable, is to say what is not 
only false but also impossible. Thus it is not the same 
thing to make a false and to make an impossible hypothesis ;^ 

15 and from the impossible hypothesis impossible results follow. 
A man has, it is true, the capacity at once of sitting and 
of standing, because when he possesses the one he also 
possesses the other ; but it does not follow that he can at 
once sit and stand, only that at another time he can do the 
other also. But ^ if a thing has for infinite time more than 
one capacity, another time is impossible and the times must 

20 coincide. Thus if anything which exists for infinite time is 
destructible, it will have the capacity of not being. Now if 
it exists for infinite time let this capacity be actualized ; ^ 
and it will be in actuality at once existent and non-existent. 
Thus a false conclusion would follow because a false assump- 
tion was made, but if what was assumed had not been 

25 impossible its consequence would not have been im- 
possible.^ 

Anything then which always exists is absolutely im- 
perishable. It is also ungenerated, since if it was generated 
it will have the power for some time of not being. For as 
that which formerly was, but now is not, or is capable at 
some future time of not being, is destructible, so that which 
is capable of formerly not having been is generated.^ But 
in the case of that which always is, there is no time for such 

30 a capacity of not being, whether the supposed time is finite 

^ Cf. AiiaL Prior. 34* I ff. for this distinction. There should be 
a colon rather than a full-stop after ahvvaTov. The production of like 
consequences is of course not peculiar to the impossible hypothesis : 
it applies equally to the false hypothesis. See loc. cit. 

^ Read d hi with FHMJ for d drj. There is no semblance of 
inference. Simplicius makes the connexion antithetical. 

■'' For eo-rni read earo) with all MSS. (except E) and Simpl. The 
fjirj dial which follows dvvarai in FHMJ must have been a copyist's 
mistake. 

'' The assumption in this case was both false and impossible. 

■' The words are taken in their ' most proper ' sense, as the qualifica- 
tion 'absolutely' in 1. 25 suggests; viz. as conveying a strict and 
demonstrable possibility or impossibility. Sec foregoing chapter. 



BOOK I. 12 281^ 

or infinite ; for its capacity of being must include the finite 
time since it covers infinite time.^ 

It is therefore impossible that one and the same thing 
should be capable of always existing and of always not- 
existing.^ And 'not always existing', the contradictory, is 
also excluded. Thus it is impossible for a thing always to 
exist and yet to be destructible. Nor, similarly, can it be 282 
generated. For of two attributes if B cannot be present 
without A^ the impossibility of A proves the impossibility 
of B. What always is^ then, since it is incapable of ever 
not being, cannot possibly be generated. But since the 
contradictory of ' that which is always capable of being ' is 5 
' that which is not always capable of being ' ; while ' that 
which is always capable of not being' is the contrary, 
whose contradictory in turn is ' that which is not always 
capable of not being ', it is necessary that the contradictories 
of both terms should be predicable of one and the same 
thing, and thus that, intermediate between what always is 
and what always is not, there should be that to which being 
and not-being are both possible ; for the contradictory of 10 
each will at times be true of it unless it always exists. 
Hence that which not always is not will sometimes be and 
sometimes not be ; and it is clear that this is true also of 
that which cannot always be but sometimes is and therefore 
sometimes is not.^ One thing, then, will have the power 
of being and of not being, and will thus be intermediate 
between the other two. 

Expressed universally our argument is as follows. Let 
there be two attributes, A and B^ not capable of being 15 
present in any one thing together, while either A or C and 

^ In 1. 29 after />i/) dvai a full-stop is required instead of a comma. 
The construction of the following clauses is difficult. The translation 
given above proceeds on the hypothesis that no stop is required after 
det ov (1. 30) and that hwarov , . . coare [xr) elvai is equivalent to dvvnTov 
Id.}} cii/ai. I cannot find another case of dwarbv wo-Te, but similar uses 
of coare are fairly common in Aristotle (see Bonitz, /nd. Ar., p. 873* 20). 
ovT (iTTHfjov ovT€ nene pao-fiivov (sc. ;^pofoi^) is a loose epexegesis of ovk 
eo-rii^ eu a xpova>, and perhaps should be preceded by a comma. 

^ Kal del jj-tj dvai is the reading of FJ Simpl. Since the omission of 
d(L in the other MSS. is easily accounted for, it seems best to accept 
this. (J at the first attempt omitted the Kai.) 

^ After TTore ov a comma, not a colon. 



282^ DE CAELO 

either.^ or D are capable of being present in everything. 
Then C and D must be predicated of everything of which 
neither A nor B is predicated. Let E lie between A and 
B ; for that which is neither of two contraries is a mean 
between them. In E both C and D must be present, for 

20 either ^ , or (7 is present everywhere and therefore in E. 
Since then A is impossible, C must be present, and the 
same argument holds of D} 

Neither that which always is, therefore, nor that which 
always is not is either generated or destructible. And clearly 
whatever is generated or destructible is not eternal. If it were, 
it would be at once capable of always being and capable of 

25 not always being, but it has already been show^n ^ that this 
is impossible. Surely then whatever is ungenerated and in 
being must be eternal, and whatever is indestructible and 
in being must equally be so." (I use the words ' ungen- 
erated ' and ' indestructible ' in their proper sense, ' un- 
generated' for that which now is and could not at any 
previous time have been truly said not to be ; ' indestruc- 
tible ' for that which now is and cannot at any future time 

30 be truly said not to be.^) If, again, the two terms are 
coincident,^ if the ungenerated is indestructible, and the in- 
destructible ungenerated, then each of them is coincident 

1 The four letters A BCD are to be allotted as follows : ^ is ' that 
which is always capable of being' = 'what always is', B is its 
contrary, ' that which is always capable of not being ' = ' what always 
is not ', C is its contradictory, ' that which is not always capable of 
being ', and D is the contradictory of B^ * that which is not always 
capable of not being '. C and D might also be described by the terms 
* what not always is ' and ' what not always is not ' respectively, 

2 28ibi8fif. 

^ The question-mark should come at the end of the line after ov hi, 
preceded by a comma at dvai. 

* i.e. each term has its third sense as defined in chapter xi 
(280^11,31). 

^ The term ' coincidence ' is used in this passage to express the 
mutual involution (called by later writers avraKoXovdia) of predicates. 
This mutual involution is here described by Aristotle in terms which 
mean that the two terms 'follow' or 'accompany' one another. But 
later on (e. g. in 282'* 10, 27, 32) he frequently says simply that one 
predicate 'follows' another when he means that the two terms are 
mutually involved. To avoid confusion I have expressed the relation 
in terms of coincidence throughout. — The ^ following the parenthesis 
introduces an alternative proof to the same effect as that which 
preceded the parenthesis. 



BOOK I. 12 282'' 

with 'eternal'; anything ungenerated is eternal and anything 282^ 
indestructible is eternal. This is clear too from the defini- 
tion of the terms. Whatever is destructible must be 
generated ; for it is either ungenerated or generated, but, if 
ungenerated, it is by hypothesis ^ indestructible. Whatever, 
further, is generated must be destructible. For it is either 
destructible or indestructible, but, if indestructible, it is by 5 
hypothesis ^ ungenerated. 

If, however, ' indestructible ' and ' ungenerated ' are not 
coincident, there is no necessity that either the ungenerated 
or the indestructible should be eternal. But they must be 
coincident, for the following reasons. The terms ' gener- 
ated ' and ' destructible ' are coincident ; this is obvious 
from our former remarks, since between what always is and 10 
what always is not there is an intermediate which is neither, 
and that intermediate is the generated and destructible. 
For whatever is either of these is capable both of being and 
of not being for a definite time: in either case, I mean, 
there is a certain period of time during which the thing is 
and another during which it is not. Anything therefore 
which is generated or destructible must be intermediate, ^i 
Now let A be that which always is and B that which 
always is not, C the generated, and D the destructible. 
Then C must be intermediate between A and B. For in 
their case there is no time in the direction of either limit,^ 
in which either A is not or B is. But for the generated 

* 281^25 ff. But Aristotle proceeds to give a proof of the mutual 
involution of these terms. If the destructible is generated and the 
generated is destructible, it follows that the ungenerated is eternal 
and the indestructible is eternal, and this is the thesis set out for proof 
in 282^ 25. But the proof here given of the antecedent depends on the 
assumption that * ungenerated ' and ' indestructible ' are coincident, 
which assumption is now proved. Aristotle's procedure, however, is 
needlessly complicated. Having proved the coincidence of ' generated ' 
and 'destructible' by assuming the coincidence of 'ungenerated' and 
' indestructible ', he now proves the coincidence of the latter by 
proving (on other lines) the coincidence of the former. 

^ i. e., in effect, ' neither in the past nor in the future '. But time, of 
course, has no limit. The notion of limit is transferred to the in- 
destructible-ungenerated from the destructible-generated. The being 
of the latter class is necessarily limited in both directions, by birth on 
one side and death on the other, and the same terms limit its not- 
being. These two limits of finite existence are used to describe the 
two directions of infinite existence. 



■0 



282^ DE CAELO 

20 there must be such a time either actually or potentially, 
though not for A and B in either way. C then will be, and 
also not be, for a limited length of time, and this is true also 
of D, the destructible. Therefore each is both generated 
and destructible. Therefore ' gtinerated ' and * destruc- 
tible ' are coincident. Now let E stand for the ungenerated, 

25 F for the generated, G for the indestructible, and H for the 
destructible. As for F and H, it has been shown that they 
are coincident. But when terms stand to one another as 
these do, F and H coincident, E and F never predicated of 
the same thing but one or other of everything, and G and 

30 H likewise, then E and G must needs be coincident. For 
suppose that E is not coincident with G, then F will be, 
since either E or F'ls predicable of everything. But of that 
of which F is predicated H will be predicable also, //"will 
283^ then be coincident with G, but this we saw to be impossible. 
And the same argument shows that G is coincident with E. 
Now the relation of the ungenerated {E) to the generated 
(F) is the same as that of the indestructible {G) to the de- 
structible {H). To say then that there is no reason why 
anything should not be generated and yet indestructible or 

S ungenerated and yet destroyed, to imagine that in the one 
case generation and in the other case destruction occurs 
once for all, is to destroy part of the data.^ For (i) every- 
thing is capable of acting or being acted upon, of being or 
not being, either for an infinite, or for a definitely limited 
space of time ; and the infinite time is only a possible alter- 
native because it is after a fashion defined, as a length of 

10 time which cannot be exceeded. But infinity in one 
direction is neither infinite nor finite. (2) Further, why, 
after always existing, was the thing destroyed, why, after 
an infinity of not being, was it generated, at one moment 
rather than another ? If every moment is alike and the 
moments are infinite in number, it is clear that a generated 
or destructible thing existed for an infinite time. It has 

' Aristotle now proceeds to apply his results to the refutation of the 
view attributed in 280*30 to Plato's Timaetis. He there promised to 
give a Clearer demonstration of its absurdity when the terms ' generated ', 
' ungenerated ', &;c. should be investigated on their own account and 
apart from the special case of the heaven. 



BOOK I. 12 283^ 

therefore for an infinite time the capacity of not being 
(since the capacity of being and the capacity of not being 15 
will be present together),^ if destructible, in the time before 
destruction, if generated, in the time after generation. If 
then we assume the two capacities to be actualized, oppo- 
sites will be present together.^ (3) Further, this second 
capacity will be present like the first at every moment, so 
that the thing will have for an infinite time the capacity 
both of being and of not being ; but this has been shown 
to be impossible.^ (4) Again, if the capacity is present prior 20 
to the activity, it will be present for all time, even while the 
thing was as yet ungenerated and non-existent, throughout 
the infinite time in which it was capable of being generated. 
At the time, then, when it was not, at that same time it had 
the capacity of being, both of being then and of being there- 
after, and therefore for an infinity of time.* 

It is clear also on other grounds that it is impossible 25 
that the destructible should not at some time be destroyed. 
For otherwise it will always be at once destructible and in 
actuality indestructible,^ so that it will be at the same time 

^ The words ai^a yap . . . KUL elvai are plainly parenthetical, since the 
TO jueV, TO Be which follow explain the clause which precedes them. 
They should be enclosed in brackets and the colon after xpovov deleted. 

^ Read a bvvaTai. Prantl's note is incorrect. The facts are as 
follows: a dvvarai. FM Simpl., a dvvavTai EL, ddvvara HJ. Bekker 
prints the last, though attested by only one of his MSS. 

^ The third argument is distinct from the second in that the second 
arrives at an abstirduin by actualizing the capacity, while the third 
points out that the co-presence of two such capacities has already 
been admitted to be impossible. Cf. 282^5, 'that which is always 
capable of being ' is the contrary of ' that which is always capable of 
not being'. Alexander seems to have maintained that our third argu- 
ment was not a distinct argument at all ; but the short account of his 
view given by Simpl. is not convincing. 

^ A colon is required after vcrrepov. Aristotle is proving that the 
capacity was present for infinite time, which in argument (3) he 
assumed as evident without proof. 

^ Prantl's note as to the reading in 1. 26 is inaccurate. The words 
Koi a<p6apTnp (not Koi (pBaprov) were lacking in the MSS. used both by 
Alexander and by Simpl, ; and they interpreted the sentence without 
those words to mean — 'it will be at once eternal and in actuality 
destructible ' ; but ' in actuality destructible ' means ' destroyed ', and 
therefore the assertion is not justified by the context. Alex., how- 
ever, suggested the insertion of the words Kal a<pdapTov, and Simpl. 
says he 'has come across ' a manuscript in which the words are found. 
Ka\ a(pdapTov seems to have been added to E upon revision, but all our 
Other MSS. have the words, and it is best to retain them in the text. 



283^ DE CAELO 

capable of always existing and of not always existing. 
Thus the destructible is at some time actually destroyed. 
The generable, similarly, has been generated, for it is capable 
of having been generated and thus also of not always 
existing.^ 
30 'We may also see in the following way how impossible it 
is either for a thing which is generated to be thenceforward 
indestructible, or for a thing which is ungenerated and has 
always hitherto existed to be destroyed. Nothing that is by 
chance can be indestructible or ungenerated, since the pro- 
283 ducts of chance and fortune are opposed to what is, or comes 
to be, always or usually, while anything which exists for a 
time infinite either absolutely or in one direction, is in exist- 
ence either always or usually. That which is by chance, then, 
is by nature such as to exist at one time and not at another. 
But in things of that character the contradictory states 
5 proceed from one and the same capacity, the matter of the 
thing being the cause equally of its existence and of its non- 
existence. Hence contradictories would be present together 
in actuality.^ 

* The end of this paragraph from Kai el yevnrov seems to be a short 
statement of the parallel argument with regard to generation. If this 
is so we require a full-stop instead of a comma after (pdaprov. to 
(pdoprov can hardly be the subject of yeyopey, as Prantl's stopping 
suggests. The last words, koI fxq ael opa etuai^ are unsatisfactory, 
since, though they draw a true consequence, it is one more directly 
appropriate to cjidopd than to yeveais. It is tempting to read koI prj ael 
apa pr) ehai. We should then have the relevant consequence and 
a more precise parallelism between the two arguments. — The point 
of the paragraph as a whole is to remove the possibility of an escape, 
by means of a doctrine of unrealized possibilities, from the conclusion 
already drawn that what is generated is also destructible. (Simpl. 
appositely quotes Twiaeus 41 a, B, where the permanence of the world- 
order depends on the will and promise of the Demiurge.) Aristotle 
always maintains that an unrealized possibility in this sense is 
inconceivable. 

^ For Prantl's Km opn read apa. The km is omitted by FMJ Simpl. — 
The notions of 'chance' [ro avroparov) and 'fortune' {jvx^ are fully 
discussed in Phys. II. iv-vi, the exclusion of the 'necessary' and the 
'usual' (283*32) being explained in II. v. It is there plainly implied 
that chance had actually been suggested by earlier writers as the 
generative cause of the world (196*33, 198*10). The reason why 
they had recourse to this notion would be that chance means a cause 
quite external to the nature of the thing considered; and thus the 
chance generation or destruction of the world would not involve the 
consequence that in general and as such the world was either generated 
or destructible. Aristotle's reply to the suggestion is simply that 
chance necessarily implies intermittent being, so that a chance- 



BOOK I. 12 283^ 

Further, it cannot truly be said of a thing now that it 
exists last year, nor could it be said last year that it exists 
now.^ It is therefore impossible for what once did not 
exist later to be eternal. For in its later state it will possess 
the capacity of not existing, only ^ not of not existing at 
a time when it exists — since then it exists in actuality — but 10 
of not existing last year or in the past. Now suppose it to 
be in actuality what it is capable of being. It will then be 
true to say now that it does not exist last year. But this is 
impossible. No capacity relates to being in the past, but 
always to being in the present or future. It is the same 
with the notion of an eternity of existence followed later 
by non-existence. In the later state the capacity will be ^5 
present for that which is not there in actuality."^ Actualize, 
then, the capacity. It will be true to say now that this 
exists last year or in the past generally. 

Considerations also not general like these but proper to 
the subject show it to be impossible that what was formerly 
eternal should later be destroyed or that what formerly was 
not should later be eternal. Whatever is destructible or 20 
generated is always alterable. Now alteration is due to 
contraries, and the things which compose the natural body 
are the very same that destroy it.'^ 

eternal is a contradiction in terms. (' Fortune ' is a name for chance 
within the sphere of conduct ; and anything which can be caused by 
chance could also, according to Aristotle, be caused either by intelli- 
gence, as in the case of conduct, or by nature, as here. See Phys. 1. c.) 

^ For eVri, IfjTiv read eVrt, tdnv. — The concluding argument is 
introduced very abruptly, by a formula which shows that in Aristotle's 
mind the suggestion here criticized is only another form of the appeal 
to chance just dealt with. The suggestion is that a capacity may be 
limited in respect of time of fulfilment. Aristotle refutes it by assuming 
that its authors admit {a) that the possessio7t of the capacity is not 
limited in time, and [b] that any capacity may be actualized. 

^ Before Tx\r]v a comma is required instead of Prantl's full-stop. 

^ ol must be taken to stand for eK€ivov 5, as in Simpl.'s paraphrase. — 
The meaning is that after the thing has ceased to be it still retains its 
capacity of existing at any time previous to that event. 

■* A comma is required after ivavrlois and, for awiaTarai, avpia-TaTat. 



BOOK II 

283** 26 ' That the heaven as a whole neither came into being i 
nor admits of destruction, as some assert, but is one and 
eternal, with no end or beginning of its total duration, con- 

30 taining and embracing in itself the infinity of time, we may 
convince ourselves not only by the arguments already set 
forth but also by a consideration of the views of those who 
differ from us in providing for its generation. If our view 
is a possible one, and the manner of generation which they 
284^ assert is impossible, this fact will have great weight in con- 
vincing us of the immortality and eternity of the world. 
Hence it is well to persuade oneself of the truth of the 
ancient and truly traditional theories, that there is some 
immortal and divine thing which possesses movement, but 

5 movement such as has no limit and is rather itself the limit 
of all other movement. A limit is a thing which contains ; 
and this motion^, being perfect, contains those imperfect 
motions which have a limit and a goal, having itself no 
beginning or end, but unceasing through the infinity of 

10 time, and of other movements, to some the cause of their 
beginning, to others offering the goal. The ancients gave 
to the Gods the heaven or upper place, as being alone im- 
mortal ; and our present argument testifies that it is inde- 
structible and ungenerated. Further, it is unaffected by 

15 any mortal discomfort, and, in addition, effortless ; for it 
needs no constraining necessity to keep it to its path, and 
prevent it from moving with some other movement more 
natural to itself. Such a constrained movement would 
necessarily involve effort — the more so, the more eternal it 
were — and would be inconsistent with perfection. Hence 
we must not believe the old tale which says that the world 

20 needs some Atlas to keep it safe — a tale composed, it would 
seem, by men who, like later thinkers, conceived of all the 

^ Omit 7/ KVKXocjwpln. The words are found only in L, and though 
harmless are quite superfluous. There is no reference to Ki;/<Xo0opia 
in Simpl.'s paraphrase. 



BOOK II. I 284^ 

upper bodies as earthy and endowed with weight, and 
therefore supported it in their fabulous way upon animate 
necessity. We must no more believe that than follow Em- 
pedocles when he says that the world, by being whirled 
round, received a movement quick enough to overpower its 25 
own downward tendency, and thus has been kept from 
destruction all this time. Nor, again, is it conceivable that 
it should persist eternally by the necessitation of a soul.^ 
For a soul could not live in such conditions painlessly or 
happily, since the movement involves constraint, being im- 30 
posed on the first body, whose natural motion is different, 
and imposed continuously.^ It must therefore be uneasy 
and devoid of all rational satisfaction ; for it could not even, 
like the soul of mortal animals, take recreation in the bodily 
relaxation of sleep. An Ixion's lot must needs possess it, 35 
without end or respite. If then, as we said, the view already 284^ 
stated of the first motion is a possible one, it is not only 
more appropriate so to conceive of its eternity, but also on 
this hypothesis alone are we able to advance a theory con- 
sistent with popular divinations of the divine nature.^ But 5 
of this enough for the present. 

2 Since there are some who say that there is a right and 
a left in the heaven^ with those who are known as Pythago- 
reans — to whom indeed the view really belongs — we must 
consider whether, if we are to apply these principles to the 
body of the universe, we should follow their statement of 10 
the matter or find a better way. At the start we may say 

1 The cosmic motions must not be regarded as imposed upon the 
body of the cosmos by a world-soul as the human soul imposes move- 
ment on the human body. Such a notion necessarily implies constraint 
on the^part of the body and effort on the part of the'soul, and there- 
fore the movement could not be eternal. Aristotle has in mind, no 
doubt, the world-soul of the Timaeus. 

"^ Read etTrep Kivei (pepeadai Tr€(f)VK6TOS . . . aXXto? kol Ktvel (Tvv€)((oij 
with all MSS. except E. Simpl.'s paraphrase supports this reading.— 
The remarks which follow as to the absence of ' rational satisfaction ' 
recall verbally Plato, Timaeus 36 E 6dav apxqv ffp^aro [17 ^vxrj — the 
world-soul] ajravaTov Ka\ e/x^poi/op jSiOU npos rov avprravTa xP'^^ou. 

^ By ' divination' (ixaureia) Aristotle means, not any religious practice 
of prophecy or the like, but simply the inspired guesses of common 
sense — rqu Koivrjv TavTTjv evuotnv rjv 6;^oju,ei/ Trept t?]s anovias Kai fxaKapio- 
Tr]Tos Tov deiov (Simpl.). 



284^ DE CAELO 

that, if right and left are applicable, there are prior princi- 
ples which must first be applied. These principles have 
been analysed in the discussion of the movements of 
animals,^ for the reason that they are proper to animal 

15 nature. For in some animals we find all such distinctions 
of parts as this of right and left clearly present, and in 
others some ; but in plants we find only above and below. 
Now if we are to apply to the heaven such a distinction of 
parts, we must expect, as we have said, to find in it also that 

20 distinction which in animals is found first of them all. 
The distinctions are three, ^ namely, above and below, front 
and its opposite, right and left — all these three oppositions 
we expect to find in the perfect body — and each may be 
called a principle. Above is the principle of length, right 

25 of breadth, front of depth. Or again we may connect them 
with the various movements, taking principle to mean that 
part, in a thing capable of movement, from which move- 
ment first begins. Growth starts from above, locomotion 
from the right, sense-movement fi'om in front (for front is 

30 simply the part to which the senses are directed). Hence 
we must not look for above and below, right and left, front 
and back, in every kind of body, but only in those which, 
being animate, have a principle of movement within them- 
selves. For in no inanimate thing do we observe a part 
from which movement originates. Some do not move at 

35 all, some move, but not indifferently in any direction ; fire, 
285^ for example, only upward, and earth only to the centre. 
It is true that we speak of above and below, right and 
left, in these bodies relatively to ourselves. The reference 
may be to our own right hands, as with the diviner, or to 
some similarity to our own members, such as the parts of 
5 a statue possess ; or we may take the contrary spatial 
order, calling right that which is to our left, and left that 
which is to our right. '^ We observe, however, in the things 

' De hicessu Anini., cc. iv, v. 

^ Prantl misprints ydv for yap. 

'■' Bekkcr and Prantl are probably right in regarding the words 
which follow ^€$u)v (viz. koI . . . ejjLTrpoadfv) as spurious, though they are 
found in all ALSS. except E. There is no trace of them in Simpl. 
or Them. 



BOOK 11. 2 285' 

themselves none of these distinctions ; indeed if they are 
turned round we proceed to speak of the opposite parts as 
right and left, above and below, front and back. Hence it 10 
is remarkable that the Pythagoreans should have spoken of 
these two principles, right and left, only, to the exclusion of 
the other four, which have as good a title as they. There 
is no less difference between above and below or front and 
back in animals generally than between right and left. 15 
The difference is sometimes only one of function,^ some- 
times also one of shape ; and while the distinction of above 
and below is characteristic of all animate things, whether 
plants or animals, that of right and left is not found in 
plants. Further, inasmuch as length is prior to breadth, if 
above is the principle of length, right of breadth, and if the 20 
principle of that which is prior is itself prior, then above 
will be prior to right, or let us say, since ' prior ' is am- 
biguous, prior in order of generation.- If, in addition, 
above is the region from which movement originates, right 
the region in which it starts, front the region to which it is 
directed, then on this ground too above has a certain original 25 
character as compared with the other forms of position. 
On these two grounds, then, they may fairly be criticized, 
first, for omitting the more fundamental principles, and 
secondly, for thinking that the two they mentioned were 
attributable equally to everything. 

Since we have already determined that functions of this 
kind belong to things which possess a principle of move- 
ment,"^ and that the heaven is animate and possesses a prin- 3° 
ciple of movement,^ clearly the heaven must also exhibit 

^ The right and left hands, for instance, differ in function but not 
in shape. It is imphed that the difference of function underlies all 
the oppositions and determines the differences of shape where these 
occur. The differences of function are summarized above, 284^25-30. 

- For the four main kinds of 'priority', see Cat. ch. xii (14=^266'".). 
Additional distinctions are made in Met, A, ch. xi. 

^ i. e. to animals. This is laid down at the beginning of the present 
chapter, 283^ 13, where reference is made to \.\\t De hicessic Animalium. 
Cf. also /'/y'j-. VIII. 4,254^7. 

* Bk. I, 279^28, where it is stated to be the source of all life and 
movement. The term 'animate' (^i\x-^vxo^) has not hitherto been 
applied to it. The notion that the stars are ' inanimate ' is rejected 
below, 292* 20. 



285^ DE CAELO 

above and below, right and left. We need not be troubled 
by the question, arising from the spherical shape of the 
world, how there can be a distinction of right and left 
285^ within it, all parts being alike and all for ever in motion. 
We must think of the world as of something in which right 
differs from left in shape as well as in other respects, which 
subsequently is included in a sphere. The difference of 
function will persist, but will appear not to by reason 
5 of the regularity of shape. In the same fashion must 
we conceive of the beginning of its movement. For even 
if it never began to move, yet it must possess a prin- 
ciple from which it would have begun to move if it had 
begun, and from which it would begin again if it came to 
a stand. Now by its length I mean the interval between 

10 its poles, one pole being above and the other below ; for 
two hemispheres are specially distinguished from all others 
by the immobility of the poles.^ Further, by ' transverse ' 
in the universe we commonly mean, not above and below, 
but a direction crossing the line of the poles, which, by 
implication, is length : for transverse motion is motion 

15 crossing motion up and down. Of the poles, that which we 
see above us is the lower region, and that which we do not 
see is the upper. For right in anything is, as we say, the 
region in which locomotion originates, and the rotation of 
the heaven originates in the region from which the stars 
rise. So this will be the right, and the region where they 

20 set the left. If then they begin from the right and move 
round to the right, the upper must be the unseen pole. For 
if it is the pole we see, the movement will be leftward, 
which we deny to be the fact. Clearly then the invisible 
pole is above. And those who live in the other hemisphere 

25 are above and to the right, while we are below and to the 
left. This is just the opposite of the view of the Pythago- 
reans, who make us above and on the right side and those 
in the other hemisphere below and on the left side ; the fact 

' The unmoving poles mark out one among the infinite possible 
bisections of the sphere as natural and intelligible. We thus arrive, 
as explained in what follows, at an 'upper' and a 'lower' hemi- 
sphere. 



BOOK II. 2 285^^ 

being the exact opposite.^ Relatively, however, to the 
secondary revolution, I mean that of the planets, we are 
above and on the right and they are below and on the left. 30 
For the principle of their movement has the reverse posi- 
tion, since the movement itself is the contrary of the other : 
hence it follows that we are at its beginning and they at its 
end. Here we may end our discussion of the distinctions 286' 
of parts created by the three dimensions and of the conse- 
quent differences of position. 

3 Since circular motion is not the contrary of the reverse 
circular motion, we must consider why there is more than 
one motion, though we have to pursue our inquiries at 5 
a distance — a distance created not so much by our spatial 
position as by the fact that our senses enable us to perceive 
very few of the attributes of the heavenly bodies. But let 

^ Heath {Aristarchus, pp. 231-2) summarizes the argument as 
follows: '"Right" is the place from which motion in space starts; 
and the motion of the heaven starts from the side where the stars rise, 
i.e. the east ; therefore the east is "right" and the west "left". If 
now (i) you suppose yourself to be lying along the world's axis with 
your head towards the north pole, your feet towards the south pole, 
and your right hand towards the east, then clearly the apparent motion 
of the stars from east to west is over your back from your right side 
towards your left ; this motion, Aristotle maintains, cannot be called 
motion " to the right ", and therefore our hypothesis does not fit the 
assumption from which we start, namely that the daily rotation '' begins 
from the right and is carried round towards the right (eVi ra ^^^la) ". 
We must therefore alter the hypothesis and suppose (2) that you are 
lying with your head towards the south pole and your feet towards the 
north pole. If then your right hand is to the east, the daily motion 
begins at your right hand and proceeds over the front of your body 
from your right hand to your left.' Heath points out that to us this 
still gives a wrong result : the motion across your front will still be 
from right to left ; but he accepts Simpl.'s explanation that movement 
to the front is regarded as rightward and motion to the back as left- 
ward — r] yap iir\ be^ia iravTOii els to efnrpoo-Oev eVri. If this is true, 
Heath's account is satisfactory. It is curious that the notion of right- 
ward movement also gives trouble in the cosmology of Plato. Heath 
has an entirely different solution of that difficulty, in which the 
ordinary sense of 'to the right' is preserved (pp. 160-3). In view of 
the solution of the present passage quoted above, perhaps there is 
something after all to be said for the assertion of Proclus (/;/ Timaeum 
220 e), quoted by Heath only to be dismissed, that eVt de^id does not 
mean els r6 be^iov but is confined to circular motion and means 'the 
direction of a movement imparted by the right hand ' {e(f) a to 8e^i6v 
Kivei). The discrimination of right and left in circular motions is 
peculiarly difficult and ambiguous, as every child knows ; and some 
such use of eVi 8e^id may have been the Greek solution of the termino- 
logical problem. 



286^ DE CAELO 

not that deter us. The reason must be sought in the 
following facts. Everything which has a function exists 
for its function. The activity of God is immortality, i. e. 

10 eternal life.^ Therefore the movement of that which is 

' divine must be eternal. But such is the heaven, viz. 
a divine body, and for that reason to it is given the circular 
body whose nature it is to move always in a circle."-^ Why, 
then, is not the whole body of the heaven of the same 
character as that part ? Because there must be something 
at rest at the centre of the revolving body ; and of that 

15 body no part can be at rest, either elsewhere or at the 
centre. It could do so only if the body's natural movement 
were towards the centre. But the circular movement is 
natural, since otherwise it could not be eternal : for 
nothing unnatural is eternal.^ The unnatural is subse- 
quent to the natural, being a derangement of the natural 

20 which occurs in the course of its generation.'* Earth then 
has to exist ; for it is earth which is at rest at the centre. 
(At present we may take this for granted : it shall be ex- 
plained later.^) But if earth must exist, so must fire. For, 
if one of a pair of contraries naturally exists, the other, if 
it is really contrary, exists also naturally. In some form it 

25 must be present, since the matter of contraries is the same. 
Also, the positive is prior to its privation (warm, for in- 
stance, to cold), and rest and heaviness stand for the priva- 

^ The argument is clear. ' God ' or ' divine ' means ' eternal '. All 
body has motion. Therefore the notion of a divine body necessarily 
involves the notion of an eternal movement. — Simpl. says wrongly that 
6e6s here stands for delov o-Mfxa. 

"^ The nature of the circular motion, and the reasons why it alone is 
compatible with immutability and the other divine attributes, have 
been explained in Bk. I, chaps, iii and iv. — The adjective * circular' 
(e'y/cuKXio?) here and in several other passages of this book is trans- 
ferred from the motion to the body endowed with it. 

° The body which is at the centre cannot be of the same nature, and 
endowed with the same motion, as that which is at the extremity ; for 
the actual position and movement of one or the other would in that 
case be unnatural. There must therefore be a body whose natural 
position is at the centre and whose natural movement is towards the 
centre. 

* All change jnvolves * derangement ' (eVo-rncrts'), Phys. 222^16: 
cf. Phys. 241'^ 2*. €K(7Taaif is opposed to reXdcoais ('fulfilment', or 
movement of a thing towards its ideal nature), Pkys. 246^17, ^2, 
247* 3. 

° See ch. xiv. 



BOOK II. 3 286^ 

tion of lightness and movement. But further, if fire and 
earth exist, the intermediate bodies ^ must exist also : for 
each element stands in a contrary relation to every other. 30 
(This, again, we will here take for granted and try later to 
explain.^) With these four elements generation clearly is 
involved, since none of them can be eternal : for contraries 
interact with one another and destroy one another. Further, 
it is inconceivable that a movable body should be eternal, 
if its movement cannot be regarded as naturally eternal : 35 
and these bodies we know to possess movement.^ Thus we 286'' 
see that generation is necessarily involved. But if so, there 
must be at least one other circular motion : for a single move- 
ment of the whole heaven would necessitate an identical re- 
lation of the elements of bodies to one another.* This matter 5 
also shall be cleared up in what follows : but for the present so 
much is clear, that the reason why there is more than one 
circular body is the necessity of generation, which follows 
on the presence of fire, which, with that of the other bodies, 
follows on that of earth ; and earth is required because 
eternal movement in one body necessitates eternal rest in 
another. 

4 The shape of the heaven is of necessity spherical ; for 10 
that is the shape most appropriate to its substance and also 
by nature primary. 

^ viz. air and water. 

"^ See De Gen. et Corr. II. iii, iv. 

^ Retaining the MSS. reading, which is confirmed by Simpl. and 
Them., tovt^v 6' 'ia-TL Kivr^ais. If these words are taken to mean ravra 
S' 6(TTi KLVTjTa, thc argumcnt, though summarily stated, is complete 
and Prantl's conjecture is unnecessary. If it is granted that the 
sublunary elements move, generation is admitted, unless it can be 
shown that their movement is such as to be naturally eternal. But 
it has already been shown {Phys, 26i'*3ifF.) that the rectilinear 
movements must be intermittent. 

^ A. is proving the necessity of the secondary revolution, i. e. that 
of the planets. ' If, he argues, ' there were only the movement of the 
fixed stars, and sun and moon were set in it and carried along with it, 
the varieties of summer and winter and the other seasons would 
disappear and the daily interchange would not follow its accustomed 
course. For if the sun were set in Cancer, we should have perpetual 
summer, and if it were set in Capricorn, perpetual winter: there 
would be no generation or destruction, not even the varied phases of 
the moon ' (Simpl.). The further discussion promised here is to be 
found in De Ge7t, et Corr. II. x. 



286^ DE CAELO 

First, let us consider generally which shape is primary 
among planes and solids alike. Every plane figure must 

15 be either rectilinear or curvilinear. Now the rectilinear is 

bounded by more than one line, the curvilinear by one only. 

.But since in any kind the one is naturally prior to the 

many and the simple to the complex, the circle will be the 

first of plane figures. Again, if by complete, as previously 

20 defined,^ we mean a thing outside which no part of itself 
can be found, and if addition is always possible to the 
straight line but never to the circular, clearly the line which 
embraces the circle is complete. If then the complete is 
prior to the incomplete, it follows on this ground also that 
the circle is primary among figures. And the sphere holds 
the same position among solids. For it alone is embraced 

25 by a single surface, while rectilinear solids have several. 
The sphere is among solids what the circle is among plane 
figures. Further, those who divide bodies into planes and 
generate them out of planes ^ seem to bear witness to the 
truth of this. Alone ^ among solids they leave the sphere 

30 undivided, as not possessing more than one surface : for the 
division into surfaces is not just dividing a whole by cutting 
it into its parts, but division of another fashion into parts 
difi'erent in form.* It is clear, then, that the sphere is first 
of solid figures. 

If, again, one orders figures according to their numbers, 

35 it is most natural to arrange them in this way. The circle 

287^ corresponds to the number one, the triangle, being the sum 

of two right angles, to the number two. But if one is 

assigned to the triangle, the circle will not be a figure 

at all. 

^ Phys. III. 207*8. For the terms of the definition cf stip. 271^ 31. 
This notion of ' perfect' (or ' complete ') is presupposed in the opening 
chapter of this treatise. — In 1. 19 read tZ>v avruv: the tcov is omitted 
only m E and F. 

^ Cf. PAys. VI. I and zn/. Bk. Ill, ch. i for further criticisms of 
these theories. The theory criticized is that expressed by Timaeus 
the Pythagorean in Plato's dialogue of that name. (So Simpl. on 
298»33.) 

^ Prantl's /jlout] is a misprint for ixopijv. 

* Both sphere and circle can of course be divided into parts, but 
they cannot be geometrically analysed into constituents not themselves 
spherical or circular. The geometrical analysis requires that the 
constituent or ' part ' shall be different in form from the whole. 



BOOK II. 4 287^ 

Now the first figure belongs to the first body, and the 
first body is that at the farthest circumference. It follows 
that the body which revolves with a circular movement 
must be spherical. The same then will be true of the body 5 
continuous with it : for that which is continuous with the 
spherical is spherical. The same again holds of the bodies 
between these and the centre. Bodies which are bounded 
by the spherical and in contact with it must be, as wholes, 
spherical ; and the bodies below the sphere of the planets 
are contiguous with the sphere above them. The sphere 
then will be spherical throughout ; for every body within it 10 
is contiguous and continuous with spheres. 

Again, since the whole revolves, palpably and by 
assumption, in a circle, and since it has been shown that 
outside the farthest circumference there is neither void nor 
place, from these grounds also it will follow necessarily that 
the heaven is spherical. For if it is to be rectilinear in 
shape, it will follow that there is place and body and void ^5 
without it. For a rectilinear figure as it revolves never 
continues in the same room, but where formerly was body, 
is now none, and where now is none, body will be in 
a moment because of the projection at the corners. 
Similarly, if the world had some other figure with unequal 20 
radii, if, for instance, it were lentiform, or oviform, in every 
case we should have to admit space and void outside the 
moving body, because the whole body would not always 
occupy the same room.^ 

Again, if the motion of the heaven is the measure of all 
movements whatever in virtue of being alone continuous 
and regular and eternal, and if, in each kind, the measure is 25 
the minimum, and the minimum movement is the swiftest, 
then, clearly, the movement of the heaven must be the 
swiftest of all movements. NoyV of lines which return upon 
themselves^ the line which bounds the circle is the shortest; 

' This depends, as Simpl. observes, after Alexander, on the position 
of the axis of revolution. In the case of a perfect sphere alone the 
position of the axis is immaterial. 

^ Reading dcf)' eavrov €({)' eavTo, with Simpl. and the consensus of the 
MSS. The Tov and t6 in Prantl's text are conjectural insertions. 
J has dcji avTov 6<^' avro. 



287^ DE CAELO 

and that movement is the swiftest which follows the 
shortest line.^ Therefore, if the heaven moves in a circle 

30 and moves more swiftly than anything else, it must 
necessarily be spherical. 

Corroborative evidence may be drawn from the bodies 
whose position is about the centre. If earth is enclosed by 
water; water by air, air by fire, and these similarly by the 
upper bodies — which while not continuous are yet contiguous 
287^ with them - — and if the surface of water is spherical, and that 
which is continuous with or embraces the spherical must 
itself be spherical, then on these grounds also it is clear 
that the heavens are spherical. But the surface of water 
5 is seen to be spherical if we take as our starting-point the 
fact that water naturally tends to collect in a hollow place — 
'hollow' meaning 'nearer the centre'. Dra^v from the 
centre the lines AB, AC, and let their extremities be joined 
by the straight line BC. The line AD, drawn to the base 
of the triangle, will be shorter than either of the radii.^ 

10 Therefore the place in which it terminates will be a hollow 
place. The water then will collect there until equality is 
established, that is until the line AE is equal to the two 
radii. Thus water forces its way to the ends of the radii, 
and there only will it rest : but the line which connects the 
extremities of the radii is circular : therefore the surface of 
the water BECis spherical. 

15 It is plain from the foregoing that the universe is 
spherical. It is plain, further, that it is turned (so to speak) 
with a finish which no manufactured thing nor anything 

^ This is true if equality of effort (aTro rr/s alrrjs 8vi'afj.eas Simpl.) is 
postulated. In a word, the underlying notion is rather the compara- 
tive economy than the comparative siuiftfiess of movements. — For the 
origin of this argument Simpl. refers to Tim. "^^"^ B. 

2 'Continuous', 'contiguous', and the related terms are defined in 
Phys. V. iii. If these bodies were continuous with the heavenly body 
they would have to move with the same motion as it. 

3 




BOOK ir. 4 287^ 

else within the range of our observation can even approach. 
For the matter of which these are composed does not 
admit of anything like the same regularity and finish as 
the substance of the enveloping body ; since with each step 20 
away from earth the matter manifestly becomes finer in the 
same proportion as water is finer than earth. 

5 Now there are two ways of moving along a circle, from A 
to B or from A to (7,^ and we have already explained ^ that 
these movements are not contrary to one another. But 
nothing which concerns the eternal can be a matter of 25 
chance or spontaneity, and the heaven and its circular 
motion are eternal. We must therefore ask why this 
motion takes one direction and not the other. Either this 
is itself an ultimate fact or there is an ultimate fact behind 
it. It may seem evidence of excessive folly or excessive zeal 
to try to provide an explanation of some things, or of every- 30 
thing, admitting no exception. The criticism, however, is not 
always just : one should first consider what reason there is 
for speaking, and also what kind of certainty is looked for, 
whether human merely or of a more cogent kind.^ When 
any one shall succeed in finding proofs of greater precision, 288^ 
gratitude will be due to him for the discovery, but at 
present we must be content with a probable solution.* If 
nature always follows the best course possible, and, just as 
upward movement is the superior form of rectilinear move- 
ment, since the upper region is more divine than the lower. 5 
so forward movement is superior to backward, then front 
and back exhibits, like rigrht and left, as we said before ^ and 



^ ^ — s. li A is the 'right from which movement starts, 

°/^ ^ « why should the movement be towards B rather than 

I J towards C ? Probably, answers Aristotle, because 

^^ — ^ movement towards B is ' forward ' and movement 

towards C ' backward ' motion. 

2 I. iv. 

^ Bekker and Prantl prefer L's KapTeptKcoTepov to the KaprepoiTepov of 
all other MSS. It is difficult to imagine why. There is good Platonic 
parallel for the use of Kaprepos in this connexion [Phaedo yy A, Theaet, 
169 B). 

* A similar caution is repeated at the beginning of ch. xii, 291^25. 
For this use of (t)aiv6p.€vov cf. Bonitz, Ind. Ar. 809*24. 

" Reading, with Prantl, e^fi S') eiVep, and accepting his punctuation. 



288^ DE CAELO 

as the difficulty just stated itself suggests, the distinction of 
prior and posterior, which provides a reason and so solves 
our difficulty. Supposing that nature is ordered in the 
10 best way possible, this may stand as the reason of the fact 
mentioned. For it is best to move with a movement simple 
and unceasing, and, further, in the superior of two possible 
directions. 

We have next to show that the movement of the heaven 6 
15 is regular and not irregular. This applies only to the first 
heaven and the first movement ; for the lower spheres 
exhibit a composition of several movements into one. If the 
movement is uneven, clearly there will be acceleration, 
maximum speed, and retardation, since these appear in all 
20 irregular motions. The maximum may occur either at the 
starting-point or at the goal or between the two ; and we 
expect natural motion to reach its maximum at the goal, 
unnatural motion at the starting-point, and missiles midway 
between the two.^ But circular movement, having no be- 

The passage as punctuated by Bekker is untranslatable. The apo- 
dosis undoubtedly begins at the word e';^^. EL give exei de e'lnep, the 
remaining MSS. e^a e'lnep. — The existence of a 'front' and 'back' in 
the world was asserted in ch. ii. The priority of *up', 'right', and 
'front' over 'down', 'left', and 'back' is assumed in the same 
chapter, 284^ 24. — The gist of the present rather involved and hesita- 
ting statement is that the only way to account for the direction of 
the heavenly movements is by means of these oppositions and the 
priority commonly attributed in each to one term over the other. 

^ It appears from Meteorologica I. iv, 341^ — 342^ that meteors and 
shooting stars come under the notion of ' missiles ' or ' things thrown '. 
Their motion is compared to that of the stone of a fruit when it is 
made to fly through the air by being squeezed out from between the 
fingers. Ordinary throwing, e. g. of a stone or javelin, would of course 
also be included. — Simpl. and, by his report, Alexander are much 
puzzled by the statement in the text. Simpl. makes the wild sugges- 
tion that A. here regards animal movements as 'missile' motion, in 
that they are neither upward nor downward but horizontal. Alex, 
suggests that ' missile ' movements may be said to have their maximum 
between goal and starting-point, because every earthly body has its 
goal either up or down, and the whole of the 'missile' movement, 
from beginning to end, takes place in the middle region. Alex, is 
probably right. It is to be remembered that all movement is either 
natural or unnatural, and that 'missile' movement can only be 
distinguished in principle as a mixture of the two ; further that the 
body thrown must be composed of one or more of the four elementary 
bodies. 'Throwing' is thought of as a forced horizontal motion put 
upon one of these bodies, each of which has a 'goal', down (or up), 
and a 'starting-point', up (or down). In such a motion the maximum 



BOOK II. 6 288^ 

ginning or limit or middle in the direct sense of the words, 
has neither whence nor whither nor middle : for in time it 
is eternal, and in length it returns upon itself without a 25 
break. If then its movement has no maximum, it can 
have no irregularity, since irregularity is produced by re- 
tardation and acceleration. Further, since everything that 
is moved is moved by something, the cause of the irregu- 
larity of movement must lie either in the mover or in the 
moved or in both. For if the mover moved not always 30 
with the same force, or if the moved were altered and did 
not remain the same, or if both were to change, the result 
might well be an irregular movement in the moved. But 
none of these possibilities can be conceived as actual in the 
case of the heavens. As to that which is moved, we have 
shown that it is primary and simple and ungenerated and 288' 
indestructible and generally unchanging ; and the mover 
has an even better right to these attributes. It is the 
primary that moves the primary, the simple the simple, 
the indestructible and ungenerated that which is indestruc- 
tible and ungenerated. Since then that which is moved, 5 
being a body, is nevertheless unchanging, how should the 
mover, which is incorporeal, be changed ? 

It follows then, further, that the motion cannot be 
irregular. For if irregularity occurs, there must be change 
either in the movement as a whole, from fast to slow and 
slow to fast, or in its parts. That there is no irregularity in 
the parts is obvious, since, if there were, some divergence 10 
of the stars would have taken place ^ before now in the 
infinity of time, as one moved slower and another faster : 
but no alteration of their intervals is ever observed. Nor 
again is a change in the movement as a whole admissible. 
Retardation is always due to incapacity, and incapacity is 
unnatural. The incapacities of animals, age, decay, and the 15 
like, are all unnatural, due, it seems, to the fact that the 

cannot be said to be attained at either terminus, since neither terminus 
is involved, but only 'between the two'. This means that in the case 
of natural motion 'goal' must be taken to be the natural place of the 
body, which is also the ' starting-point ' of unnatural motion in the 
same body. In 'throwing', therefore, there is neither starting-point 
nor goal, but all is in the intermediate region. 
^ For y^yov^i read e-yeyoVet with FHLMJ. 



288'^ DE CAELO 

whole animal complex is made up of materials which differ 
in respect of their proper places, and no single part occupies 
its own place. If therefore that which is primary contains 

20 nothing unnatural, being simple and unmixed and in its 
proper place and having no contrary, then it has no place 
for incapacity, nor, consequently, for retardation or (since 
acceleration involves retardation) for acceleration. Again, 
it is inconceivable that the mover should first show in- 
capacity for an infinite time, and capacity afterwards for 
another infinity. For clearly nothing which, like incapacity, 

25 is unnatural ever continues for an infinity of time ; nor does 
the unnatural endure as long as the natural, or any form of 
incapacity as long as the capacity.^ But if the movement 
is retarded it must necessarily be retarded for an infinite 
time.- Equally impossible is perpetual acceleration or 
perpetual retardation. For such movement would be in- 
finite and indefinite,^ but every movement, in our view, 

50 proceeds from one point to another and is definite in 
character. Again, suppose one assumes a minimum time 
in less than which the heaven could not complete its move- 
ment. For, as a given walk or a given exercise on the harp 
cannot take any and every time, but every performance has 
its definite minimum time which is unsurpassable, so, one 
might suppose, the movement of the heaven could not be 
289^ completed in any and every time. But in that case per- 
petual acceleration is impossible (and, equally, perpetual 
retardation : for the argument holds of both and each),"^ 

1 Reading old' oXco?, with all MSS. except E, which PrantI follows 
in reading ov8' oXXco?. — The effect of aWco^ is to make the unnatural 
one species or department within the general notion of incapacity. 
oAoj? has much more varied uses and enables one to avoid this 
implication. 

^ i.e. equality of duration must be supposed between the incapacity 
(retardation) and the preceding capacity, as assumed in the foregoing 
argument, in which infinity (sc. in one direction) is attributed to each. 
For if the speed of movement has been everlastingly increasing, and 
now begins to decrease, it is impossible to suppose anything else but 
that it will decrease everlastingly. 

" viz. in respect of its speed. The hypothesis now considered is 
retardation or acceleration not balanced by its opposite but having 
neither beginning nor end, i.e. infinite in do//i directions. 

* Prantl's stopping needs correction. The words d 8e f^fJ . . . OiWepov 
should be enclosed within brackets. 



BOOK II. 6 289' 

if we may take acceleration to proceed by identical or in- 
creasing additions of speed and for an infinite tinae. The 
remaining alternative is to say that the movement exhibits 5 
an alternation of slower and faster : but this is a mere 
fiction and quite inconceivable. Further, irregularity of 
this kind would be particularly unlikely to pass unobserved, 
since contrast makes observation easy. 

That there is one heaven, then, only, and that it is un- 
generated and eternal, and further that its movement is 
regular, has now been sufficiently explained. 10 

7 We have next to speak of the stars, as they are called, 
of their composition, shape, and movements. It would be 
most natural and consequent upon what has been said that 
each of the stars should be composed of that substance in 15 
which their path lies,^ since, as we said, there is an element 
whose natural movement is circular. In so saying we are 
only following the same line of thought as those who say 
that the stars are fiery because they believe the upper body 
to be fire, the presumption being that a thing is composed of 
the same stuff as that in which it is situated. The warmth 
and light which proceed from them are caused by the friction ao 
set up in the air by their motion. Movement tends to 
create fire in wood, stone, and iron ; and with even more 
reason should it have that effect on air, a substance which is 
closer to fire than these.^ An example is that of missiles, 
which as they move are themselves fired so strongly that 
leaden balls are melted ; and if they are fired the surround- 35 
ing air must be similarly affected. Now while the missiles 
are heated by reason of their motion in air, which is turned 
into fire by the agitation produced by their movement,^ 
the upper bodies are carried on a moving sphere, so that, 
though they are not themselves fired, yet the air underneath 30 
the sphere of the revolving body is necessarily heated by its 

^ i. e. of the same substance as the spheres to which their motion 
is due. 

^ A colon is required after the word drjp in 1. 23. 

^ iT>^r}yrj seems to stand here for the continuous beating of the 
missile upon the air rather than for a single blow. Cf. Simpl. 439. 25 
vnb r^y . . . TrXrjyi^s Ka\ napaTpi-yj/ecos. The same use recurs below, 
291^ 17. 



289^ DE CAELO 

motion, and particularly in that part where the sun is 
attached to it.^ Hence warmth increases as the sun gets 
nearer or higher or overhead. Of the fact, then, that the 
35 stars are neither fiery nor move in fire, enough has been 
said. 

289^ Since changes evidently occur not only in the position of 8 
the stars but also in that of the whole heaven, there are 
three possibilities. Either (i) both are at rest, or (2) both 
are in motion, or (3) the one is at rest and the other in 
motion. 

(i) That both should be at rest is impossible; for, if the 

5 earth is at rest, the hypothesis does not account for the 

observations ; and we take it as granted that the earth is at 

rest. It remains either that both are moved, or that the 

one is moved and the other at rest. 

(2) On the view, first, that both are in motion, we have the 
absurdity that the stars and the circles move with the same 
speed, i. e. that the pace of every star is that of the circle in 
10 which it moves. For star and circle are seen to come back 
to the same place at the same moment ; from which it 
follows that the star has traversed the circle and the circle 
has completed its own movement, i. e. traversed its own 
circumference, at one and the same moment. But it is 
difficult to conceive that the pace of each star should be 
15 exactly proportioned to the size of its circle. That the pace 
of each circle should be proportionate to its size is not 
absurd but inevitable : but that the same should be true of 
the movement of the stars contained in the circles is quite 

1 The stars are not themselves ignited because the substance of 
which they are composed cannot be transmuted into any other as fire, 
air, and the other sublunary substances can. It is, however, legitimate 
to object to the above account that fire, not air, is the substance in 
contact with the spheres, and that only with the innermost. How, 
then, is air ignited by the movement of the spheres ? Alex, and 
Simpl. agree that ' air' must in some sense include fire (or we/cKau/Ma, 
the ' fuel of fire ' which occupies the outer place) ; but that, even if 
true, will not solve the difficulties. The view here advanced is 
nowhere fully worked out ; but some further suggestions are made 
in Meteor. I. iii and iv. Cf. Heath, Aristarchus, pp. 241-2. It seems 
certain that what Aristotle meant was that the 'fire' which is in 
contact with the spheres is ignited and agitated by their motion and 
the air beneath by it (341-'^ 2-3 and 30-31). 



BOOK II. 8 289^ 

incredible. For if, on the one hand, we suppose that the 
star which moves on the greater circle is necessarily swifter, 
clearly we also admit that if stars shifted their position so 
as to exchange circles, the slower would become swifter and 20 
the swifter slower. But this would show that their move- 
ment was not their own, but due to the circles. If, on the 
other hand, the arrangement was a chance combination, the 
coincidence in every case of a greater circle with a swifter 
movement of the star contained in it is too much to believe. 
In one or two cases it might not inconceivably fall out so, 25 
but to imagine it in every case alike is a mere fiction. 
Besides, chance has no place in that which is natural, and 
what happens everywhere and in every case is no matter of 
chance. 

(3) The same absurdity is equally plain -^ if it is supposed 
that the circles stand still and that it is the stars them- 
selves which move. For it will follow that the outer stars 
are the swifter, and that the pace of the stars corresponds to 3^ 
the size of their circles. 

Since, then, we cannot reasonably suppose either that 
both are in motion or that the star alone moves, the remain- 
ing alternative is that the circles should move, while the stars 
are at rest and move with the circles to which they are 
attached. Only on this supposition are we involved in no 
absurd consequence. For, in the first place, the quicker 
movement of the larger circle is natural when all the circles 35 
are attached to the same centre. Whenever bodies are 290' 
moving with their proper motion, the larger moves 
quicker. It is the same here with the revolving bodies: 
for the arc intercepted by two radii will be larger in the 
larger circle, and hence it is hot surprising that the 
revolution of the larger circle should take the same time as 5 
that of the smaller. And secondly, the fact that the 
heavens do not break in pieces follows not only from this 

^ Bekker and Prantl read ravra instead of ra avrd, which is the 
reading of all MSS. and of Simpl. The alteration is unnecessary. 
The difficulty is the same as that pointed out in the preceding argu- 
ment — an unaccountable correspondence between the size of the circle 
and the speed of the star's movement. 

F 2 



290^ DE CAELO 

but also from the proof already given ^ of the continuity 
of the whole. 

Again, since the stars are spherical, as our opponents 

assert and we may consistently admit, inasmuch as we 

' construct them out of the spherical body, and since the 

lo spherical body has two movements proper to itself, namely 
rolling and spinning,^ it follows that if the stars have a 
movement of their own, it will be one of these. But neither 
is observed, (i) Suppose them to spin. They would then 
stay where they were, and not change their place, as, by ob- 
servation and general consent, they do. Further, one would 
expect them all to exhibit the same movement : but the 

15 only star which appears to possess this movement is the 
sun, at sunrise or sunset, and this appearance is due not to 
the sun itself but to the distance from which we observe it. 
The visual ray being excessively prolonged becomes weak 
and wavering.^ The same reason probably accounts for the 
apparent twinkling of the fixed stars and the absence of 

20 twinkling in the planets. The planets are near, so that the 
visual ray reaches them in its full vigour, but when it 
comes to the fixed stars it is quivering because of the dis- 
tance and its excessive extension ; and its tremor produces 
an appearance of movement in the star : for it makes no 
difference whether movement is set up in the ray or in the 
object of vision. 

25 (2) On the other hand, it is also clear that the stars 
do not roll. For rolling involves rotation : but the * face ', 

^ Cf. c. iv. But there is no attempt to prove continuity in the 
De Caelo. 

^ By 'spinning' is meant rotation on a stationary axis, by 'rolling' 
a forward movement in which a body turns completely round in 
a distance equal to its own circumference. See Heath, Aristarchics^ 
pp. 233-5. 

•^ The term o\//'ts- ( = visual ray) belongs to pre-Aristotelian psychology. 
Cf Plato, Meno, 76 C-D. Aristotle's use of it here and elsewhere 
(e.g. Meteor. III. iv, 373^*2) seems to commit him 'to the view that 
the eye sees by rays issuing from a native fire within it' (Beare, 
Greek Theories of Elementary Cogtiition, p. 66, n. 1). But his own 
argument, when dealing with vision, is to the contrary effect. 'In 
seeing. we take something in, not give something out' {Top. 105^6); 
and the process is 'from object to eye, not conversely' (Beare, p. 86). 
Aristotle must be supposed here to be adopting popular or Platonic 
terminology. 



BOOK II. 8 290' 

as it is called, of the moon is always seen.^ Therefore, 
since any movement of their own which the stars possessed 
would presumably be one proper to themselves, and no such 
movement is observed in them, clearly they have no move- 
ment of their own. 

There is, further, the absurdity that nature has bestowed 30 
upon them no organ appropriate to such movement. For 
nature leaves nothing to chance, and would not, while car- 
ing for animals, overlook things so precious. Indeed, 
nature seems deliberately to have stripped them of every- 
thing which makes self-originated progression possible, and 
to have removed them as far as possible from things which 
have organs of movement. This is just why it seems 35 
proper that the whole heaven and every star should be 290^ 
spherical. For while of all shapes the sphere is the most 
convenient for movement in one place, making possible, as 
it does, the swiftest and most self-contained motion, for 
forward movement it is the most unsuitable, least of all 5 
resembling shapes which are self-moved, in that it has no 
dependent or projecting part, as a rectilinear figure has, and 
is in fact as far as possible removed in shape from ambu- 
latory bodies. Since, therefore, the heavens have to move 
in one place, and the stars are not required to move them- 
selves forward, it is natural that both should be spherical — 10 
a shape which best suits the movement of the one and the 
immobility of the other. 

9 From all this it is clear that the theory that the move- 
ment of the stars produces a harmony, i. e. that the sounds 
they make are concordant, in spite of the grace and 
originality with which it has been stated, is nevertheless 15 
untrue.'' Some thinkers suppose that the motion of bodies 

^ It has been objected to Aristotle that if the moon always shows 
the same side to us it is thereby proved that it does rotate upon its 
axis. But such rotation (incidental, in Aristotle's view, to the move- 
ment of the sphere) is quite different from the rotation involved in 
'rolling', which Aristotle is here concerned to deny. See Heath, 
p. 235. 

^ The doctrine of the 'harmony of the spheres' is no doubt, as 
Simpl. says, Pythagorean. The most famous statement of the doctrine 
is in Plato's Republic (Myth of Er, 617B), and the ratios given to the 
planets in Tiviaeus, 35B, seem to have a musical significance. For 
a discussion of the doctrine see Heath, A?ista?rh2(s, pp. 105-15. 



290^ DE CAELO 

of that size must produce a noise,, since on our earth the 
motion of bodies far inferior in size and in speed of move- 
ment has that effect. Also, when the sun and the moon, 
they say, and all the stars, so great in number and in size, 

20 are moving with so rapid a motion, how should they not 
produce a sound immensely great ? Starting from this 
argument and from the observation that their speeds, as 
measured by their distances, are in the same ratios as 
musical concordances, they assert that the sound given 
forth by the circular movement of the stars is a harmony. 
Since, however, it appears unaccountable that we should 

25 not hear this music, they explain this by saying that the 
sound is in our ears from the very moment of birth and is 
thus indistinguishable from its contrary silence, since sound 
and silence are discriminated by mutual contrast. What 
happens to men, then, is just what happens to coppersmiths, 
who are so accustomed to the noise of the smithy that it 

30 makes no difference to them. But, as we said before, 
melodious and poetical as the theory is, it cannot be a true 
account of the facts. There is not only the absurdity of our 
hearing nothing, the ground of which they try to remove, 
but also the fact that no effect other than sensitive is 
produced upon us. Excessive noises, we know, shatter the 

35 solid bodies even of inanimate things : the noise of thunder, 
291^ for instance, splits rocks and the strongest of bodies. But 
if the moving bodies are so great, and the sound which 
penetrates to us is proportionate to their size, that sound 
must needs reach us in an intensity many times that of 
thunder, and the force of its action must be immense. 
5 Indeed the reason why we do not hear, and show in our 
bodies none of the effects of violent force, is easily given : 
it is that there is no noise. But not only is the explanation 
evident ; it is also a corroboration of the truth of the views 
we have advanced. For the very difficulty which made 
the Pythagoreans say that the motion of the stars produces 

10 a concord corroborates our view. Bodies which are them- 
selves in motion, produce noise and friction : but those 
which are attached or fixed to a moving body, as the parts 
to a ship, can no more create noise, than a ship on a river 



BOOK II. 9 291 

moving with the stream. Yet by the same argument one 
might say it was absurd that on a large vessel the motion of 
mast and poop should not make a great noise, and the like 15 
might be said of the movement of the vessel itself But sound is 
caused when a moving body is enclosed in an unmoved body, 
and cannot be caused by one enclosed in, and continuous with, 
a moving body which creates no friction. We may say, 
then, in this matter that if the heavenly bodies moved in 
a generally diffused mass of air or fire, as every one supposes, 20 
their motion would necessarily cause a noise of tremendous 
strength and such a noise would necessarily reach and 
shatter us.^ Since,, therefore, this effect is evidently not 
produced, it follows that none of them can move with the 
motion either of animate nature or of constraint.^ It is as 
though nature had foreseen the result, that if their move- 25 
ment were other than it is, nothing on this earth could 
maintain its character. 

That the stars are spherical and are not self-moved, has 
now been explained. 

10 With their order — I mean the position of each, as 30 
involving the priority of some and the posteriority of 
others, and their respective distances from the extremity — 
with this astronomy may be left to deal, since the astro- 
nomical discussion is adequate.^ This discussion shows 
that the movements of the several stars depend, as regards 
the varieties of speed which they exhibit, on the distance 

^ Prantl misprints dLaKvaiev for diaKiaL^iv. 

- If the stars moved in a non-moving medium either with a self- 
originated motion, like that of an animal, or with a motion imposed 
on them by external force, like that of a stone thrown, a great and 
destructive noise would result. There is no such noise or destruction. 
Therefore they do not so move. The Pythagorean doctrine is thus 
used to corroborate a conclusion already reached. It might be 
objected that Aristotle has already postulated friction with another 
substance to account for the brightness of the stars, and that this 
friction might well be expected to be accompanied with noise as in 
the case of missiles on the earth. 

^ The tone of this reference to " astronomy', as well as the present 
tense in the verb Xeyenu, suggest that Aristotle is not here referring to 
other works of his own but to contemporary' works on astronomy, 
current in the school, by other writers. These sentences also clearly 
imply that 'astronomy' is more empirical in its methods than the 
Dt; Caelo. Cf. infra, 291^21. — In 1. 29 Prantl's o is a misprint for ov. 



291^ DE CAELO 

35 of each- from the extremity. It is established that the 
outermost revolution of the heavens is a simple movement 
291^ and the swiftest of all, and that the movement of all other 
bodies is composite and relatively slow, for the reason that 
each is moving on its own circle with the reverse motion to 
that of the heavens. This at once leads us to expect that 
the body which is nearest to that first simple revolution 
5 should take the longest time to complete its circle, and that 
which is farthest from it the shortest, the others taking 
a longer time the nearer they are and a shorter time the 
farther away they are. For it is the nearest body which is 
most strongly influenced, and the most remote, by reason 
of its distance, which is least affected, the influence on the 
intermediate bodies varying, as the mathematicians show, 

10 with their distance.^ 

With regard to the shape of each star, the most reasonable 11 
view is that they are spherical. It has been shown ^ that 
it is not in their nature to move themselves, and, since 
nature is uq wanton or random creator, clearly she will have 
15 given things which possess no movement a shape particularly 
unadapted to movement. Such a shape is the sphere, since 
it possesses no instrument of movement. Clearly then 
their mass will have the form of a sphere.^ Again, what 

^ In regard to 'order' Aristotle only seeks to explain one point 
which might present a difficulty. It would be natural to expect the 
moon, which is the nearest planet to the earth, to have the slowest 
motion; but in fact it is the swiftest of the planets. His answer is 
that the movement of the planets, being the reverse of that of the 
outer heaven, is hampered by proximity to it ; and the planet nearest 
to the earth is least influenced and therefore moves swiftest. Simpl. 
raises the objection: is not the planetary motion then in some degree 
constrained or unnatural ? He quotes with approval from Alex, the 
reply : ' No : for the planetary sphere is not unwilling. This accords 
with its purpose and desire. It may be necessity, but it is also good, 
and recognized as such.' Simpl. is not altogether satisfied by this 
solution. 

^ Ch. viii. 

'•' Simpl. notes a circle in Aristotle's argument, since he has already 
used the spherical shape of the stars to prove that they have no 
independent motion (c. viiij. (The same charge is brought against 
Aristotle by Dreyer, P/anefary Sjystews, p. in.) He is not satisfied 
with Alex.'s rejoinder that neither of these arguments stands alone. 
The true .answer is that the argument of c. viii is explicitly based, in 
respect of the spherical shape of the stars, on a premise borrowed 
from the opposition : see 290** 7. Aristotle's own proof of the matter 
precedes it. This argument is therefore in order. 



BOOK II. II 291^ 

holds of one holds of all, and the evidence of our eyes shows 
us that the moon is spherical. For how else should the 
moon as it waxes and wanes show for the most part 20 
a crescent-shaped or gibbous figure, and only at one mo- 
ment a half-moon? And astronomical arguments^ give 
further confirmation ; for no other hypothesis accounts for 
the crescent shape of the sun's eclipses. One, then, of the 
heavenly bodies being spherical, clearly the rest will be 
spherical also. 

12 There are two difficulties, which may very reasonably 
here be raised, of which we must now attempt to state the 25 
probable solution : ^ for we regard the zeal of one whose 
thirst after philosophy leads him to accept even slight 
indications where it is very difficult to see one's way, as 
a proof rather of modesty than of over-confidence. 

Of many such problems one of the strangest is the 
problem why we find the greatest number of movements in 30 
the intermediate bodies, and not, rather, in each successive 
body a variety of movement proportionate to its distance 
from the primary motion. For we should expect, since the 
primary body shows one motion only, that the body which 
is nearest to it should move with the fewest movements, 
say two, and the one next after that with three, or some 
similar arrangement. But the opposite is the case. The 35 
movements of the sun and moon are fewer than those of 292^ 
some of the planets. Yet these planets are farther from 
the centre and thus nearer to the primary body than they, 
as observation has itself revealed. For we have seen the 
moon, half-full, pass beneath the planet Mars, which 5 
vanished on its shadow side and came forth by the bright 
and shining part.^ Similar accounts of other stars are 

^ See note on 291^32. 

■' See note on 288^^2. 

" Brandis (Berlin Aristotle, vol. IV, 497^13) quotes a scholium to 
the effect that Alexander in his Commentary said it was Mercury, not 
Mars. Both Simpl. and Them., however, give Mars without question. 
If it was ^lars, a calculation of Kepler's {Asti'otiomia Nova^ 1609, 
p. 323) fixes the date. ' Inveni,' he writes, Mongissima inductione per 
annos L, ab anno quindecimo ad finem vitae Aristotelis, non potuisse 
esse alio die, quam in vespera diei IV Aprilis, anno ante CHRISTI 
vulgarem epocham CCCLVil, cum Aristoteles XXi annorum audiret 



292^ DE CAELO 

given by the Egyptians and Babylonians, whose observa- 
tions have been kept for very many years past, and from 
whom much of our evidence about particular stars is 
derived.^ 

TO ' A second difficulty which may with equal justice be 
raised is this. Why is it that the primary motion includes 
such a multitude of stars that their whole array seems to 
defy counting, while of the other stars ^ each one is separated 
off, and in no case do we find two or more attached to the 
same motion ? ^ 

On these questions, I say, it is well that we should seek 

15 to increase our understanding, though we have but little to 
go upon, and are placed at so great a distance from the 
facts in question. Nevertheless there are certain principles 
on which if we base our consideration we shall not find this 
difficulty by any means insoluble. We may object that we 
have been thinking of the stars as mere bodies, and as units 

20 with a serial order indeed but entirely inanimate ; but 
\ should rather conceive them as enjoying life and action. 
On this view the facts cease to appear surprising. For it is 
natural that the best-conditioned of all things should have 
its good without action, that that which is nearest to it 
should achieve it by little and simple action, and that which 
is farther removed by a complexity of actions, just as with 

25 men's bodies one is in good condition without exercise at 
all, another after a short walk, while another requires 
running and wrestling and hard training,* and there are yet 

Eudoxum, ut ex Diogene Laertio constat.' Diogenes' date for 
Aristotle's birth is in fact 01. 99, i (384-3 B, C.) : Aristotle would 
therefore be 27 at the date arrived at. The calculation for Mercury 
does not appear to have been made. 

* See note on 270'^ 14. 

^ i. e. the planets. 

^ The term (popd (motion) is transferred from the motion itself to the 
sphere which imparts the motion. 

^ There seems to be no parallel for the use of the word Kopiais 
(tr. 'hard training'} in connexion with the exercises of the palaestra, 
though Kouiarpa is used in post-Aristotelian writers for the arena. 
Simpl. says the term stands for the training of the wrestler, dia to ev 
K(>v(L yviiva^eaOai tu TruXutaTpiKa. By water {/. of I^hil. xxviii, p. 241) 
objects that the third term in the phrase should be a distinct form of 
exercise from running or wrestling, and suggests /cfj/co^^nVfca?. Perhaps 
it is best to keep the text, though there can be no certainty that it is 
right. 



BOOK II. 12 292' 

others who however hard they worked themselves could 
never secure this good, but only some substitute for it. To 
succeed often or in many things is difficult. For instance, 
to throw ten thousand Coan throws with the dice would be 30 
impossible, but to throw one or two is comparatively easy."^ 
In action, again, when A has to be done to get B^ B to 
get C, and C to get D, one step or two present little 
difficulty, but as the series extends the difficulty grows- 292 
We must, then, think of the action of the lower stars as 
similar to that of animals and plants. For on our earth 
it is man that has the greatest variety of actions — for there 
are many goods that man can secure ; hence his actions are 
various ^ and directed to ends beyond them — while the 
perfectly conditioned has no need of action, since it is itself 5 
the end, and action always requires two terms, end and 
means. The lower animals have less variety of action than 
man ; and plants perhaps have little action and of one kind 
only.^ For either they have but one attainable good (as 
indeed man has), or, if several, each contributes directly to 10 
their ultimate good.* One thing then has and enjoys the 



^ Prantl's Kwow? rests on one MS. (H) and was known as an alterna- 
tive reading to Simpl. Two MSS. (EL) give Xt'ous, two others (FM) 
XiQv^ rj KMovs. J has ;^tXiou? ;^coXoi/s', with x^^'^s V Kot^ovs in the margin. 
Simp], thinks the point is the size of the dice {cos /jteydXcov da-TpaydXoov 
iv dp.(^0T€paL9 yivofxevcov rats vtj(tols), Prantl takes the impossibiHty to 
be a succession of good throws or ' sixes ', and therefore prefers 
' Coan ' to ' Chian ', which according to Polhix was used for the worst 
throw. The impossibility is clearly the same whether the worst throw 
or the best is intended ; but, since success is implied by the context, 
I have followed Prantl. The double reading YJovs rj K<oovs may how- 
ever be right. 

^ Reading TrpdrTei, with FHMT and Bekker, for Prantl's TrpdrTav 
(EL). 

^ The long parenthesis (1. 3 uoWciiv ydp to 1. 7 eVe/ca) in Prantl's text 
breaks the structure of the sentence and should be removed. The 
succession of colons which results (for a colon must be marked after 
Trpd^eiy^in 1. 3) is best broken by placing full-stops after cf)uToov (1. 2), 
ev(Ka (1. 4), eveKa (1. 7). 

* If there is more than one good, e. g. nutriment and propagation, 
each is a constituent of the plant's ' good ' in the final sense. To be 
able to accept something merely as a means to something else, i.e. as 
indirectly good, is a distinctive mark of a higher development. Thus 
the variety here indicated as characteristic of human action lies not 
so much in the superior range of human desires (though that also is 
a fact) as in the variety and complexity of the means by which man 
effects their satisfaction. 



292^ DE CAELO 

ultimate good, other things attain to it, one immediately ^ 
by few steps, another by many, while yet another does not 
even attempt to secure it but is satisfied to reach a point 
not far removed from that consummation. Thus, taking 
health as the end, there will be one thing that always 
possesses health, others that attain it, one by reducing 
flesh, another by running and thus reducing flesh, another 

15 by taking steps to enable himself to run, thus further 
increasing the number of movements, while another cannot 
attain health itself, but only running or reduction of flesh, 
so that one or other of these is for such a being the end.^ 
For while it is clearly best for any being to attain the real 
end, yet, if that cannot be, the nearer it is to the best the 

20 better will be its state. It is for this reason that the earth 
moves not at all and the bodies near to it with few move- 
ments. For they do not attain the final end, but only come 
as near to it as their share in the divine principle permits.^ 
But the first heaven finds it immediately with a single 

25 movement, and the bodies intermediate between the first 
and last heavens attain it indeed, but at the cost of a multi- 
plicity of movement.* 

As to the difficulty that into the one primary motion 
is crowded a vast multitude of stars, while of the other 
stars each has been separately given special movements 
of its own, there is in the first place this reason for regarding 
the arrangement as a natural one. In thinking of the life 

^ Reading eldvs for iyyvs. Cf. 1. 20 below, iyym is in all the 
MSS., but is quite intolerable in view of the general contrast between 
attainment and approximation made here and repeated below. The 
influence of e-y-yu? in the following line may be supposed to have 
caused its substitution for evOvs here. Simp), paraphrases to be bi 
()\iy<jiv Kivijaecou (i(piKUilTai Trpos to invTov TeXos, and therefore appears 
not to have had e'yyvs in his text. Them., however, has it : ' ad illud 
prope per pauca accedit.' 

'^ Place a full-stop after eXBe'ip (1, 13), delete bracket, comma after 
laxvavOrivai (1. 1 7). ' Running' or ' reduction of flesh ' becomes in such 
a case the 'end', i.e. the content of purpose, as soon as the true end 
or good is recognized as unattainable. 

^ Simpl. finds this sentence difficult. He did not see that Aristotle 
here, as frequently elsewhere, uses aWd where aXX' fj would be 
expected. See lionitz, Ind. Ar. 33^^ 15. 

^ The upshot of the argument seems to be this, that the earth and 
the bodies nearest to it move simply, or not at all, because they are 
content with little, and perfection is beyond their reach. 



BOOK II. 12 292^ 

and moving principle of the several heavens one must 
regard the first as far superior to the others. Such 30 
a superiority would be reasonable. For this single first 
motion has to move many of the divine bodies, while the 
numerous other motions move only one each, since each 293^ 
single planet moves with a variety of motions. Thus, then, 
nature makes matters equal and establishes a certain order, 
giving to the single motion many bodies and to the single 
body many motions. And there is a second reason why 
the other motions have each only one body, in that each of 5 
them except the last, i. e. that which contains the one star,^ 
is really moving many bodies. For this last sphere moves 
with many others, to which it is fixed, each sphere being 
actually a body ; so that its movement will be a joint 
product. Each sphere, in fact, has its particular natural 
motion, to which the general movement is, as it were, 10 
added. But the force of any limited body is only adequate 
to moving a limited body.^ 

The characteristics of the stars which move with a circular 
motion, in respect of substance and shape, movement and 
order, have now been sufficiently explained. 

13 It remains to speak of the earth, of its position, of the 15 
question whether it is at rest or in motion, and of its shape. 
I. As to its position there is some difference of opinion. 
Most people — all, in fact, who regard the whole heaven as 
finite — say it lies at the centre. But the Italian philoso- 20 
phers known as Pythagoreans take the contrary view. At 
the centre, they say, is fire, and the earth is one of the stars, 
creating night and day by its circular motion about the 

^ The movements of each planet are analysed into the combination 
of a number of simple spherical motions each contributed by a single 
sphere. The ' last ' sphere or motion means the outermost, viz. that 
to which the planet is actually attached. The inner spheres have 
really bodies to move even though they carry no planet : for they 
have to communicate their motion to the sphere or spheres in which 
they are included. 

^ Prantl seems to find unnecessary difficulty in this sentence. 
These spheres, says Aristotle, have only a limited force, and they 
have enough to do to impart their motion to the outer spheres, and 
through it to the planet : the burden of several planets would be too 
much for them. 



293^ DE CAELO 

centre. They further construct another earth in opposition 

25 to ours to which they give the name counter-earth.^ In all 
this they are not seeking for theories and causes to account 
for observed facts, but rather forcing their observations and 
trying to accommodate them to certain theories and 
opinions of their own. But there are many others who 
would agree that it is wrong to give the earth the central 

30 position, looking for confirmation rather to theory than to 
the facts of observation. Their view is that the most 
precious place befits the most precious thing : but fire, they 
say, is more precious than earth, and the limit than the 
intermediate, and the circumference and the centre are 
limits. Reasoning on this basis they take the view that it 
is not earth that lies at the centre of the sphere, but rather 
293 fire. The Pythagoreans have a further reason. They hold 
that the most important part of the world, which is the 
centre, should be most strictly guarded, and name it, or 
rather the fire which occupies that place, the ' Guard-house 
of Zeus ', as if the word 'centre' were quite unequivocal, 
5 and the centre of the mathematical figure were always the 
same with that of the thing or the natural centre. But it is 
better to conceive of the case of the whole heaven as 
analogous to that of animals, in which the centre of the 
animal and that of the body are different. For this reason 
they have no need to be so disturbed about the world, or to 

10 call in a guard for its centre : rather let them look for the 
centre in the other sense and tell us what it is like and 
where nature has set it. That centre will be something 
primary and precious ; but to the mere position we should 
give the last place rather than the first. For the middle is 
what is defined, and what defines it is the limit, and that 
which contains or limits is more precious than that which 

15 is limited, seeing that the latter is the matter and the 
former the essence of the system. 

II. As to the position of the earth, then, this is the view 

which some advance, and the views advanced concerning 

its rest or motion are similar. For here too there is no 

general agreement. All who deny that the earth lies at 

^ ovo\ia is omitted by FHMJ, but is probably right. 



BOOK II. 13 293 



the centre think that it revolves about the centre,^ and not 
the earth only but, as we said before, the counter-earth as 20 
well. Some of them even consider it possible that there 
are several bodies so moving, which are invisible to us 
owing to the interposition of the earth. This, they say, 
accounts for the fact that eclipses of the moon are more 
frequent than eclipses of the sun : for in addition to the 
earth each of these moving bodies can obstruct it. Indeed, 35 
as in any case the surface of the earth is not actually 
a centre but distant from it a full hemisphere, there is no 
more difficulty, they think, in accounting for the observed 
facts on their view that we do not dwell at the centre, than 
on the common view that the earth is in the middle.- Even 
as it is, there is nothing in the observations to suggest that 
we are removed from the centre by half the diameter of the 30 
earth. Others, again, say that the earth, which lies at the 
centre, is ' rolled ', and thus in motion, about the axis of 
the whole heaven. So it stands written in the Timaeiis? 

III. There are similar disputes about the sJiape of the 
earth. Some think it is spherical, others that it is flat and 
drum-shaped. For evidence they bring the fact that, as the 294' 

^ /i7;S' in 1. 18 appears to prove that the comma should be put 
after KeTa-Oai instead of after avrrjv, and that (f)a(jiv governs both 
infinitives. 

^ Prantl's insertion of ht] in the last clause rests on a misunder- 
standing of the passage. The text is quite sound.— Dreyer {Planetary 
Systems, p. 45) thinks that the supposed movement would seriously 
affect observations of the sun and the moon. 

^ Timaeus, 40 B, For a discussion of this vexed passage see 
Heath, Aristarchus, pp. 174-8. J has eiKfinOai koI Kiveladai (in 
296* 26, however, where the sam.e pair of words recur, it has elWeadai 
K. K.), which decreases the probability, not antecedently very great, 
that the words koI Knveia-Oai are an insertion. Unless the idea of 
movement is contained in the phrase, the quotation would seem to 
be out of place here. It seems plain that Aristotle considered the 
word IWeadaL ('rolled' in the text) obscure or ambiguous, and added 
the words Ka\ Kivs'icrdaL to indicate his interpretation of it. Alex. 
{apiid Simpl.) says that the word used in the Timaeus means 
'pressed' [didCeadaL), but that it is difficult to contradict Aristotle 
on a point on which he was so much better informed. Simpl. says 
that, spelt with the diphthong et and a single A, the word does 
connote rotation. He points out that Aristotle promised to speak of 
the earth's motion and rest \ and suggests that, taking Ka\ Kive'iadru to 
be a later insertion, one might suppose that Aristotle passes in this 
sentence to the consideration of the view that the earth is at rest. 
But this will hardly do. 



294''^ DE CAELO 

sun rises and sets, the part concealed by the earth shows 
a straight and not a curved edge, whereas if the earth were 
spherical the line of section would have to be circular. In 

5 this they leave out of account the great distance of the sun 
from the earth and the great size of the circumference, 
which, seen from a distance on these apparently small 
circles appears straight. Such an appearance ought not to 
make them doubt the circular shape of the earth. But they 
have another argument. They say that because it is at 

10 rest, the earth must necessarily have this shape. For there 
are many different ways in which the movement or rest of 
the earth has been conceived. 

The difficulty must have occurred to every one. It would 
indeed be a complacent mind that felt no surprise that, 
while a little bit of earth, let loose in mid-air, moves and 

15 will not stay still, and the more there is of it the faster it 
moves, the whole earth, free in mid-air, should show no 
movement at all. Yet here is this great weight of earth, 
and it is at rest. And again, from beneath one of these 
moving fragments of earth, before it falls, take away the 
earth, and it will continue its downward movement with 
nothing to stop it. The difficulty then, has naturally passed 

20 into a commonplace of philosophy ; and one may well 
wonder that the solutions offered are not seen to involve 
greater absurdities than the problem itself. 

By these considerations some have been led to assert 
that the earth below us is infinite, saying, with Xenophanes 
of Colophon, that it has ' pushed its roots to infinity ',^ — in 
order to save the trouble of seeking for the cause. Hence 

25 the sharp rebuke of Empedocles, in the words ' if the deeps 
of the earth are endless and endless the ample ether — such 
is the vain tale told by many a tongue, poured from the 
mouths of those who have seen but little of the whole '.^ 

^ Diels, Vorsokratiker^ , ii A47 (53, 38 ff.), B 28 (63, 8). Ritter and 
Preller, 103 b. Simpl. cannot find the quotation in the writings of 
Xenophanes, and doubts whether to /carto r)]'i 7?ji- means ' the under- 
parts of the carlh' or 'the ether under the earth'. A fragment 
corroborating the former interpretation survives (no. 28 in Diels). 
Cf. Burnet, E.G.P.^ § 60. 

^ Diels, Vors? 21 13 39 (241, 16). Ritter and Preller, 103 b. Burnet, 
E.G.P.3 p. 212. 



BOOK II. 13 294^ 

Others say the earth rests upon water. This, indeed, is the 
oldest theory that has been preserved, and is attributed to 
Thales of Miletus. It was supposed to stay still because it 30 
floated like wood and other similar substances, which are 
so constituted as to rest upon water but not upon air. As 
if the same account had not to be given of the water which 
carries the earth as of the earth itself ! It is not the nature 
of water, any more than of earth, to stay in mid-air : it 
must have something to rest upon. Again, as air is lighter 294^ 
than water, so is water than earth : how then can they think 
that the naturally lighter substance lies below the heavier ? 
Again, if the earth as a whole is capable of floating upon 
water, that must obviously be the case with any part of it. 
But observation shows that this is not the case. Any piece 5 
of earth goes to the bottom, the quicker the larger it is. 
These thinkers seem to push their inquiries some way into 
the problem, but not so far as they might. It is what we 
are all inclined to do, to direct our inquiry not by the 
matter itself, but by the views of our opponents : and even 
when interrogating oneself one pushes the inquiry only 10 
to the point at which one can no longer offer any opposi- 
tion. Hence a good inquirer will be one who is ready in 
bringing forward the objections proper to the genus, and 
that he will be when he has gained an understanding of all 
the differences.^ 

Anaximenes and Anaxagoras and Democritus give the 
flatness of the earth as the cause of its staying still. Thus, 15 
they say, it does not cut, but covers like a lid, the air 
beneath it. This seems to be the way of flat-shaped 
bodies : for even the wind can scarcely move them because 
of their power of resistance. The same immobility, they 
say, is produced by the flatness of the surface which the 
earth presents to the air which underlies it ; while the air, 



^ The objections must be ' proper to the kind ' or class to which the 
subject of investigation belongs, i.e. scientific, not dialectical or 
sophistical. These thinkers, as Simpl. observes, have failed to investi- 
gate the peculiar characteristics of wood and earth in the genus 
'body', and therefore think that, because wood floats, earth may. 
For the importance of a study of the ' differences ' Simpl. refers to 
Top. I. xviii. 

645.20 G 



294^ DE CAELO 

20 not having room enough to change its place because it is 

underneath the earth, stays there in a mass, like the water 

in the case of the water-clock.^ And they adduce an 

amount of evidence to prove that air, when cut off and at 

- rest, can bear a considerable weight. 

Now, first, if the shape of the earth is not flat, its flat- 
ness cannot be the cause of its immobility. But in their 

25 own account it is rather the size of the earth than its flat- 
ness that causes it to remain at rest. For the reason why 
the air is so closely confined that it cannot find a passage, 
and therefore stays where it is, is its great amount : and 
this amount is great because the body which isolates it, the 
earth, is very large. This result, then, will follow, even if 

30 the earth is spherical, so long as it retains its size. So far 
as their arguments go, the earth will still be at rest. 

In general, our quarrel with those who speak of move- 
ment in this way cannot be confined to the parts ^; it con- 
cerns the whole universe. One must decide at the outset 
whether bodies have a natural movement or not, whether 
there is no natural but only constrained movement. Seeing, 
295^ however, that we have already decided this matter to the 
best of our ability, we are entitled to treat our results as 
representing fact. Bodies, we say, which have no natural 
movement, have no constrained movement ; and where 
there is no natural and no constrained movement there will 
5 be no movement at all. This is a conclusion, the necessity 
of which we have already decided,^ and we have seen 
further that rest also will be inconceivable, since rest, like 

^ Reading wa-nep with the MSS. Diels {Vors.^ 2S, 32) inserts roC 
before fxeTaa-Trjvai (1. 19), a conjecture which has some support in L, 
which has nov in that place. — Experiments with the water-clock are 
frequently mentioned. See esp. Emped. fr. 100 (Diels), Arist. Probl. 
914'' 26, Purnet, E.G.P.^ Index I s.v. Klepsydra. 'The water-clock', 
says Simpl., 'is a vessel with a narrow mouth and a flattish base 
pierced with small holes, what we now call a Jiydrarpax. If this 
vessel is dipped in water while the mouth at the top is kept closed, 
no water runs in through the holes. The massed air inside resists 
the water and prevents its ingress, being unable to change its own 
place. When the mouth at the top is opened the water runs in, the 
air making way for it.' The position of the water beneath the water- 
clock is analogous to that of the air beneath the earth. 

^ i. e. to the single element earth or to earth and air. 

^ I. ii-iv. 



I 



BOOK II. 13 295^ 

movement, is either natural or constrained. But if there is 
any natural movement, constraint will not be the sole prin- 
ciple of motion or of rest. If, then, it is by constraint that 
the earth now keeps its place, the so-called ' whirling ' 
movement by which its parts came together at the centre 10 
was also constrained. (The form of causation supposed 
they all borrow from observations of liquids and of air, 
in which the larger and heavier bodies always move 
to the centre of the whirl. This is thought by all those 
who try to generate the heavens to explain why the earth 
came together at the centre. They then seek a reason for its 15 
staying there ; and some say, in the manner explained, that 
the reason is its size and flatness, others, with Empedocles, 
that the motion of the heavens, moving about it at a higher 
speed, prevents movement of the earth, as the water in 
a cup, when the cup is given a circular motion, though it is 20 
often underneath the bronze, is for this same reason pre- 
vented from moving with the downward movement which 
is natural to it.^) But suppose both the ' whirl ' and its 
flatness (the air beneath being withdrawn -) cease to pre- 
vent the earth's motion, where will the earth move to then ? 
Its movement to the centre was constrained, and its rest at 
the centre is due to constraint ; but there must be some 
motion which is natural to it. Will this be upward motion 25 
or downward or what ? It must have some motion ; and if 
upward and downward motion are alike to it, and the air 
above the earth does not prevent upward movement, then 
no more could air below it prevent downward movement. 
For the same cause must necessarily have the same efl"ect 
on the same thing. •'^ 

Further, against Empedocles there is another point which 30 
might be made. When the elements were separated off by 

^^ Simplicius seems to be right in considering the portion included 
within brackets in the text as a parenthetic note on divrja-is, interrupt- 
ing Aristotle's argument. 

-' The sense required is * withdrawn ', as above, but there is no 
parallel to the use of vrrfXdetv in this sense. The MSS. offer no 
variant, and Simpl. paraphrases eKaravTos. In the absence of a better 
suggestion I should read vTre^e\df>pTos. 

^ The suggestion clearly is that, consciously or unconsciously, these 
thinkers attributed a natural motion downward to the earth, since 
they gave it a reason for not moving in that direction only. 

G 2 



295^ DE CAELO 

Hate, what caused the earth to keep its place ? Surely the 
* whirl * cannot have been then also the cause. It is absurd 
too not to perceive that, while the whirling movement may 
have been responsible for the original coming together of 
the parts of earth at the centre, the question remains, why 
35 now do all heavy bodies move to the earth. For the whirl 
295^ surely does not come near us. Why, again, does fire move 
upward ? Not, surely, because of the whirl. But if fire is 
naturally such as to move in a certain direction, clearly the 
same may be supposed to hold of earth. Again, it cannot 
be the whirl which determines the heavy and the light.^ 
5 Rather that movement caused the pre-existent heavy and 
light things to go to the middle and stay on the surface 
respectively. Thus, before ever the whirl began, heavy and 
light existed ; and what can have been the ground of their 
distinction, or the manner and direction of their natural 
movements? In the infinite chaos there can have been 
neither above nor below, and it is by these that heavy and 
light are determined.' 
10 It is to these causes that most writers pay attention : but 
there are some, Anaximander, for instance, among the 
ancients, who say that the earth keeps its place because of 
its indifference.^ Motion upward and downward and side- 
ways were all, they thought, equally inappropriate to that 
which is set at the centre and indifferently related to every 
15 extreme point ; and to move in contrary directions^ at the 
same time was impossible : so it must needs remain still. 
This view is ingenious but not true. The argument would 
prove that everything, whatever it be, which is put at the 



^ Read Ka\ to Kovcpov with all MSS. except E. 

^ Literally 'likeness'. Kranz, Index to Diels, Vors.y s. v. ofxoioTTjs, 
translates * gleichmassige Lage '. Burnet (who formerly took a dif- 
ferent view) now accepts ' indifference ' as the equivalent of SfxoioTTjs 
in this passage. (E.G.P.^ p. 66, n. i.) Cf. Burnet's note on Plato, 
Phaedo, 109 A 2, where he proposes the translation ' equiformity ', 
and the phrase 7rp6y o/iioiViy ytavia^ below (296^ 20). From Aris- 
totle's wording it seems probable that he had the Phaedo in mind 
here. The full phrase there is : tj]v ofxoioTrjTa tov olpavov avrov 
(dVTco TfuvTT] Kdl Trjs yrjS (WTtjs rrju lanppmridv. It is to be observed that 
Plato makes ofimoTrjs an attribute of the whole heaven or universe, not 
of the^^earth. 

" Prantl's ivavrlov is a misprint for ivavriov. 



BOOK II. 13 295^ 

centre, must stay there. Fire, then, will rest at the centre : 
for the proof turns on no peculiar property of earth. But 
this does not follow. The observed facts about earth are 20 
not only that it remains at the centre, but also that it moves 
to the centre. The place to which any fragment of earth 
moves must necessarily be the place to which the whole 
moves ; and in the place to which a thing naturally moves, 
it will naturally rest. The reason then is not in the fact 
that the earth is indifferently related to every extreme 
point : for this would apply to any body, whereas move- 25 
ment to the centre is peculiar to earth. Again it is absurd 
to look for a reason why the earth remains at the centre 
and not for a reason why fire remains at the extremity. If 
the extremity is the natural place of fire, clearly earth must 
also have a natural place. But suppose that the centre is 
not its place, and that the reason of its remaining there is this 30 
necessity of indifference — on the analogy of the hair which, 
it is said, however great the tension, will not break under 
it, if it be evenly distributed, or of the man who, though 
exceedingly hungry and thirsty, and both equally,-^ yet 
being equidistant from food and drink, is therefore bound 
to stay where he is — even so, it still remains to explain why 35 
fire stays at the extremities. It is strange, too, to ask 296^ 
about things staying still but not about their motion, — why, 
I mean, one thing, if nothing stops it, moves up, and another 
thing to the centre. Again, their statements are not true. 
It happens, indeed, to be the case that a thing to which 5 
movement this way and that is equally inappropriate is 
obliged to remain at the centre.^ But so far as their argu- 
ment goes, instead of remaining there, it will move, only not 
as a mass but in fragments. For the argument applies 
equally to fire. Fire, if set at the centre, should stay there, 
like earth, since it will be indifferently related to every point 10 
on the extremity. Nevertheless it will move, as in fact it 
always does move when nothing stops it, away from the 
centre to the extremity. It will not, however, move in a 

^ The structure of the sentence would be made clearer if commas 
were placed after /xeV and after fie in 1. 33. 

^ The principle is in fact true, if it is properly understood, i.e. seen 
to apply, as explained in what follows, only to indivisible bodies. 



296^ DE CAELO 

mass to a single point on the circumference — the only pos- 
sible result on the lines of the indifference theory — but 

15 rather each corresponding portion of fire to the correspond- 
ing part of the extremity, each fourth part, for instance, to 
a fourth part of the circumference. For since no body is 
a point, it will have parts. The expansion, when the body 
increased the placaijoccupied, would be on the same prin- 
ciple as the contraction, in which the place was diminished. 
Thus, for all the indifference theory shows to the contrary, 

20 earth also would have moved in this manner away from the 
centre, unless the centre had been its natural place. 

We have now outlined the views held as to the shape, 
position, and rest or movement of the earth. 

Let us first decide the question whether the earth moves 14 

25 or is at rest. For, as we said, there are some who make it 

one of the stars, and others who, setting it at the centre, 

suppose it to be ' rolled ' and in motion about the pole as 

axis.^ That both views are untenable will be clear if we 

take as our starting-point the fact that the earth's motion, 

whether the earth be at the centre or away from it, must 

30 needs be a constrained motion. It cannot be the movement 

of the earth itself. If it were, any portion of it would have 

this movement ; but in fact every part moves in a straight 

line to the centre. Being, then, constrained and unnatural, 

the movement could not be eternal. But the order of the 

universe is eternal. Again, everything that moves with the 

35 circular ifiovement, except the first sphere, is observed to 

296^ be passed, and to move with more than one motion. The 

earth, then, also, whether it move about the centre or as 

stationary at it, must necessarily move with two motions. 

But if this were so, there would have to be passings and 

5 turnings of the fixed stars. Yet no such thing is observed. 

The same stars always rise and set in the same parts of the 

earth. '^ 

' For 'iWfaOuL J has e'lKXeaOui. See note on 293^31. 

^ This passage is examined in Heath, Ar/s/arc/ius, pp. 240-1. The 
necessity for two motions appears to rest only on the analogy of the 
planets, which are * passed ' or left behind by the motion of the sphere 
of the fixed stars. The consequence, that there would be variety in 



I 



BOOK II. 14 296^ 

Further, the natural movement of the earth, part and 
whole alike, is to the centre of the whole — whence the fact 
that it is now actually situated at the centre — but it might 
be questioned, since both centres are the same, which centre 10 
it is that portions of earth and other heavy things move to. 
Is this their goal because it is the centre of the earth or 
because it is the centre of the whole ? The goal, surely, 
must be the centre of the whole. For fire and other light 
things move to the extremity of the area which contains 
the centre. It happens, however, that the centre of the 15 
earth and of the whole is the same. Thus they do move 
to the centre of the earth, but accidentally, in virtue of the 
fact that the earth's centre lies at the centre of the whole. 
That the centre of the earth is the goal of their movement 
is indicated by the fact that heavy bodies moving towards 
the earth do not move parallel but so as to make equal 20 
angles,^ and thus to a single centre, that of the earth. It is 
clear, then, that the earth must be at the centre and im- 
movable, not only for the reasons already given, but also 
because heavy bodies forcibly thrown quite straight upward 
return to the point from which they started, even if they 
are thrown to an infinite distance.^ From these considera- 25 
tions then it is clear that the earth does not move and does 
not lie elsewhere than at the centre. 

From what we have said the explanation of the earth's 
immobility is also apparent. If it is the nature of earth, as 
observation shows, to move from any point to the centre, as 

the places of rising and setting of the fixed stars, follows from the 
assumption of a second motion, if the second is taken to be oblique to 
the first (Heath, loc. cit.). 

^ i. e. at right angles to a tangent : if it fell otherwise than at right 
angles, the angles on each side of the line of fall would be unequal. 
Cf. inf. 311^34, where the argument is repeated. The phrase irpbs 
ofxoias yaviaf, ' at like angles ', appears to strike Simpl. as a rather 
strange equivalent for npos 'laas ycovias, ' at e^ua/ angles ', borrowed, as 
he says, from those who referred ' angle ' to the category of quality — 
ojjLoias 8e ckoXovv tos I'cra? ycovcas ol tijv ycoviav vno to ■noiov-di'dyoPTes 
(538, 22). Cf Burnet's remarks on ofxoiorrjs in Phaedo, 109 A 2, quoted 
in part above in note on 295^ 11. 

'^ It seems plain that the words Ka-xa arddfju^v ('quite straight') refer 
to the line of the throw, not, as Simpl. supposes, to the line of return. 
But it is difficult to see what independent test Aristotle had of the 
straightness of the throw. 



296^ DE CAELO 

of fire contrariwise to move from the centre to the extremity, 

30 it is impossible that any portion of earth should move away 
from the centre except by constraint. For a single thing 
has a single movement, and a simple thing a simple : con- 
trary movements cannot belong to the same thing, and 
movement away from the centre is the contrary of movement 
to it. If then no portion of earth can move away from the 
centre, obviously still less can the earth as a whole so move. 

35 For it is the nature of the whole to move to the point to 
297^ which the part naturally moves. Since, then, it would 
require a force greater than itself to move it, it must needs 
stay at the centre. This view is further supported by the 
contributions of mathematicians to astronomy, since the 
5 observations made as the shapes change by which the order 
of the stars is determined,^ are fully accounted for on the 
hypothesis that the earth lies at the centre. Of the position 
of the earth and of the manner of its rest or movement, our 
discussion may here end. 
( Its shape must necessarily be spherical. For every por- 

10 tion of earth has weight until it reaches the centre, and the 
jostling of parts greater and smaller would bring about not 
a waved surface, but rather compression and convergence ^ 
of part and part until the centre is reached. The process 
should be conceived by supposing the earth to come into 
being in the way that some of the natural philosophers 

15 describe.^ Only they attribute the downward movement 
to constraint, and it is better to keep to the truth and say 
that the reason of this motion is that a thing which possesses 

' The sense of the sentence is, clearly, 'the phenomena are accounted 
for on the present hypothesis: why change it?' But the precise 
relevance of (apparent) changes of shape does not seem clear. Simpl. 
illustrates by changes which would be necessitated by the hypothesis 
of a moving earth ; but his own paraphrase of Aristotle's words 
implies that the changes in question are observed changes. The 
Greek implies (i) that the order of the stars is settled by the apparent 
shapes or patterns which they make in combination ; (2) that the 
changes of these shapes are accounted for on the hypothesis of a 
stationary earth. 

* avyxwpdv is clearly used here of ' convergence ', not, as Prantl 
translates, of 'making way'. So Simpl. paraphrases, o-u/xTrAaTTerat 
Tj (rvyx(>>l)(t. erepnv irepM. 

^ i'he cosmogony which follows is in principle that of Anaxagoras 
(r.urnet, E.G. P.'' § 133). 



1 



BOOK II. 14 297^ 

weight is naturally endowed with a centripetal movement. 
When the mixture, then, was merely potential, the things 
that were separated off moved similarly from every side 
towards the centre. Whether the parts which came together 
at the centre were distributed at the extremities evenly, or 20 
in some other way, makes no difference. If, on the one 
hand, there were a similar movement from each quarter of 
the extremity to the single centre, it is obvious that the 
resulting mass would be similar on every side. For if an 
equal amount is added on every side the extremity of the 
mass will be everywhere .equidistant from its centre, i.e. the 25 
figure will be spherical. ; But neither will it in any way 
affect the argument if there is not a similar accession of 
concurrent fragments from every side. For the greater 
quantity, finding a lesser in front of it, must necessarily 
drive it on, both having an impulse whose goal is the centre, 
and the greater weight driving the lesser forward till this 30 
goal is reached. In this we have also the solution of a pos- 
sible difficulty. The earth, it might be argued, is at the 
centre and spherical in shape : if, then, a weight many times 
that of the earth were added to one hemisphere, the centre 
of the earth and of the whole will no longer be coincident. 
So that either the earth will not stay still at the centre, or 
if it does, it will be at rest without having its centre at the 297^ 
place to which it is still its nature to move.^ Such is the 
difficulty. A short consideration will give us an easy 
answer, if we first give precision to our postulate that any 
body endowed with weight, of whatever size, moves towards 
the centre. Clearly it will not stop when its edge touches 5 
the centre. The greater quantity must prevail until the 
body's centre occupies the centre. For that is the goal of 
its impulse. Now it makes no difference whether we apply 

^ The words 'at the centre ' in the first clause seem intrusive at first 
sight ; and logically they are indefensible. ' Either the earth will not 
stay still at the centre, or, if it does stay still at the centre, it will not 
have its (new) centre at the centre which is its natural goal ! ' The 
words enl tov /jtea-ov, then, may be an insertion. They are, however, 
more probably due to the desire for a direct contradictory. The view 
is ixevei eVi rou [xearov : the contradictory is therefore ov ixevei enl tov 
fxeaov : and the drrep recalls only the fxevet. ' Either it does not stay 
still at the centre or it doesn't stay still at the ce7it7-e' 



297'' DE CAELO 

this to a clod or common fragment of earth or to the earth 
as a whole. The fact indicated does not depend upon 

10 degrees of size but applies universally to everything that 
has the centripetal impulse. Therefore earth in motion, 
whether in a mass or in fragments, necessarily continues to 
move until it occupies the centre equally every way, the 
less being forced to equalize itself by the greater owing to 
the forward drive of the impulse.^ 

If the earth was generated, then, it must have been 

15 formed in this way, and so clearly its generation was 
spherical ; and if it is ungenerated and has remained so 
always, its character must be that which the initial genera- 
tion, if it had occurred, would have given it. But the 
spherical shape, necessitated by this argument, follows also 
from the fact that the motions of heavy bodies always 

20 make equal angles,^ and are not parallel. This would be 
the natural form of movement towards what is naturally 
spherical. Either then the earth is spherical or it is at 
least naturally spherical.^ And it is right to call anything 
that which nature intends it to be, and which belongs to it, 
rather than that which it is by constraint and contrary to 
nature. The evidence of the senses further corroborates 
this. How else would eclipses of the moon show segments 

25 shaped as we see them ? As it is, the shapes which the 
moon itself each month shows are of every kind — straight, 
gibbous, and concave — but in eclipses the outline is always 
curved : and, since it is the interposition of the earth that 

^ The argument is quite clear if it is understood that 'greater' and 
* less ' here and in * 30 and in ^ 5 stand for greater and smaller portions 
of one body, the line of division passing through the centre which is 
the goal. Suppose the earth so placed in regard to the centre. The 
larger and heavier division would ' drive the lesser forward ', i. e. 
beyond the centre (^ 30) ; it would ' prevail until the body's centre 
occupied the centre' {^ s) ■> i^ would 'force the less to equalize itself, 
i. e. to move on until the line passing through the central goal divided 
the body equally. Simpl. fails to see this. — Alex. {ap. Simpl. 543, 15) 
raises the difficulty that the final movement of the ' less ' will be away 
from the centre, or upward, and hence unnatural. But this is to make 
a perverse abstraction of part from whole. The desire of earth to 
reach the centre can never be fully satisfied, since the centre is 
a geometrical point. 

^ See note on 296'' 20. 

" Allowing for scruples due to the evident inequalities of the earth's 
surface. 



BOOK II. 14 297^ 

makes the eclipse, the form of this line will be caused by 30 
the form of the earth's surface, which is therefore spherical. 
Again, our observations of the stars make it evident, not 
only that the earth is circular, but also that it is a circle of 
no great size. For quite a small change of position to 
south or north causes a manifest alteration of the horizon. 
There is much change, I mean, in the stars which are over- 298' 
head, and the stars seen are different, as one moves north- 
ward or southward. Indeed there are some stars seen in 
Egypt and in the neighbourhood of Cyprus which are not 
seen in the northerly regions ; and stars, which in the north 5 
are never beyond the range of observation, in those regions 
rise and set. All of which goes to show not only that the 
earth is circular in shape, but also that it is a sphere of no 
great size : for otherwise the effect of so slight a change of 
place would not be so quickly apparent. Hence one should 
not be too sure of the incredibility of the view of those who 10 
conceive that there is continuity between the parts about 
the pillars of Hercules and the parts about India, and that 
in this way the ocean is one. As further evidence in favour 
of this they quote the case of elephants, a species occurring 
in each of these extreme regions, suggesting that the 
common characteristic of these extremes is explained by 15 
their continuity. Also, those mathematicians who try to 
calculate the size of the earth's circumference arrive at the 
figure 400,000 stades.^ This indicates not only that the 
earth's mass is spherical in shape, but also that as compared 
with the stars it is not of great size. 20 

^ Simpl. gives, for the benefit of ' those who doubt the wisdom of 
the ancients', a summary account of the methods by which this result 
was attained. — This appears to be the oldest recorded estimate of the 
size of the earth. 400,000 stades = 9,987 geographical miles. Other 
estimates (in miles) are: Archimedes, 7,495; Eratosthenes and Hip- 
parchus, 6,292; Poseidonius, 5,992 or 4,494; present day, 5,400. 
(These figures are borrowed from Prantl's note on the passage in his 
translation, p. 319.) 



BOOK III 

298^ We have already discussed the first heaven and its parts, i 

25 the moving stars within it, the matter of which these are 
composed and their bodily constitution, and we have also 
shown that they are ungenerated and indestructible. Now 
things that we call natural are either substances or functions 
and attributes of substances. As substances I class the 

30 simple bodies — fire, earth, and the other terms of the 
series — and all things composed of them ; for example, 
the heaven as a whole and its parts, animals, again, and 
plants and their parts. By attributes and functions I mean 
the movements of these and of all other things in which 
they have power in themselves to cause movement, and 
298 also their alterations and reciprocal transformations. It is 
obvious, then, that the greater part of the inquiry into 
nature concerns bodies : for a natural substance is either 
a body or a thing which cannot come into existence without 
5 body and magnitude. This appears plainly from an analysis 
of the character of natural things, and equally from an 
inspection of the instances of inquiry into nature. Since, 
then, we have spoken of the primary element, of its bodily 
constitution, and of its freedom from destruction and 
generation, it remains to speak of the other two.^ In 
speaking of them we shall be obliged also to inquire into 

10 generation and destruction. For if there is generation 
anywhere, it must be in these elements and things com- 
posed of them. 

This is indeed the first question we have to ask : is 
generation a fact or not ? Earlier speculation was at 
variance both with itself and with the views here put for- 

15 ward as to the true answer to this question. Some removed 
generation and destruction from the world altogether. 

' Aristotle speaks of the four sublunary elements as two, because 
generically they are two. Two are heavy, two light : two move up 
and two down. Books III and IV of this treatise deal solely with 
these elements. 



BOOK III. I 298^ 

Nothing that is, they said, is generated or destroyed, and 
our conviction to the contrary is an illusion. So maintained 
the school of Melissus and Parmenides. But however 
excellent their theories may otherwise be, anyhow they 
cannot be held to speak as students of nature. There may 
be things not subject to generation or any kind of move- 
ment, but if so they belong to another and a higher inquiry 20 
than the study of nature. They, however, had no idea of 
any form of being other than the substance of things per- 
ceived ; and when they saw, what no one previously had 
seen, that there could be no knowledge or wisdom without 
some such unchanging entities, they naturally transferred 
what was true of them to things perceived. Others, perhaps 
intentionally, maintain precisely the contrary opinion to 25 
this. It had been asserted that everything in the world 
was subject to generation and nothing was ungenerated, 
but that after being generated some things remained in- 
destructible while the rest were again destroyed. This had 
been asserted in the first instance by Hesiod and his 
followers, but afterwards outside his circle by the earliest 
natural philosophers.^ But what these thinkers maintained 
was that all else has been generated and, as they said, ' is 30 
flowing away', nothing having any solidity, except one 
single thing which persists as the basis of all these trans- 
formations. So we may interpret the statements of 
Heraclitus of Ephesus and many others.^ And some ^ sub- 
ject all bodies whatever to generation, by means of the 
composition and separation of planes. 299' 

Discussion of the other views may be postponed.'* But 
this last theory which composes every body of planes is, as 

^ The reference, according to Simplicius, is to Orphic writings {' the 
school of Orpheus and Musaeus '). 

^ e.g. Thales, Anaximander, Anaximenes. 

" ' The view of Timaeus the Pythagorean, recorded by Plato in the 
dialogue named after him' (Simpl.). The theory criticized is certainly 
that advanced in the Tzmaeus, and is usually attributed to Plato, as 
by Zeller, PA. d. Gr} II. i, p. 804, but Aristotle probably has also in 
mind certain members of the Academy, particularly Xenocrates 
(zA, pp. ioi6fr.). 

■* The promised discussion is not to be found in the De Caelo nor in 
its sequel, the De Generaiio7ie et Corruptione. But Aristotle has 
already devoted some attention to these views at the beginning of the 
Physics^ and there is also the discussion of Met. A. 



299^ DE CAELO 

the most superficial observation shows, in many respects in 
plain contradiction with mathematics. It is, however, wrong 

5 to remove the foundations of a science unless you can replace 
them with others more convincing. And, secondly, the same * 
theory which composes solids of planes clearly composes 
planes of lines and lines of points, so that a part of a line 
need not be a line. This matter has been already considered 

10 in our discussion of movement, where we have shown that 
an indivisible length is impossible.^ But with respect to 
natural bodies there are impossibilities involved in the 
view which asserts indivisible lines, which we may briefly 
consider at this point. For the impossible consequences 
which result from this view in the mathematical sphere will 
reproduce themselves when it is applied to physical bodies, 

1 5 but there will be difficulties in physics which are not present 
in mathematics ; for mathematics deals with an abstract 
and physics with a more concrete object. There are many 
attributes necessarily present in physical bodies which are 
necessarily excluded by indivisibility ; all attributes, in fact, 
which are divisible.^ There can be nothing divisible in an 
indivisible thing, but the attributes of bodies are all divisible 

2o in one of two ways. They are divisible into kinds, as colour 
is divided into white and black, and they are divisible per 
accidens when that which has them is divisible. In this 
latter sense attributes which are simple^ are nevertheless 
divisible. Attributes of this kind will serve, therefore, to 
illustrate the impossibility of the view. It is impossible, if 

35 two parts of a thing have no weight, that the two together 
should have weight. But either all perceptible bodies 
or some, such as earth and water, have weight, as these 
thinkers would themselves admit. Now if the point has no 
weight, clearly the lines have not either, and, if they have 
not, neither have the planes. Therefore no body has 

30 weight. It is, further, manifest that their point cannot have 

' Phys. VI. i. 

'^ The reading duHpeTou, though preserved only in one rather inferior 
manuscript, must be preferred on grounds of sense to the adiaiperov 
of the other manuscripts. The silence of Simphcius seems to cor- 
roborate the reading diaiperoi/. Possibly the clause is a gloss. 

^ i. e. not divisible into kinds. 



BOOK III. I 299^ 

weight. For while a heavy thing may always be heavier 
than something and a light thing lighter than something, 299^ 
a thing which is heavier or lighter than something 
need not be itself heavy or light, just as a large thing is 
larger than others, but what is larger is not always large. 
A thing which, judged absolutely, is small may none the 
less be larger than other things. Whatever, then, is heavy 5 
and also heavier than something else, must exceed this by 
something which is heavy. A heavy thing therefore is 
always divisible. But it is common ground that a point is 
indivisible. Again, suppose that what is heavy is a dense 
body, and what is light rare. Dense differs from rare in 
containing more matter in the same cubic area. A point, 
then, if it may be heavy or light, may be dense or rare. 10 
But the dense is divisible while a point is indivisible. And 
if what is heavy must be either hard or soft, an impossible 
consequence is easy to draw. For a thing is soft if its 
surface can be pressed in, hard if it cannot ; and if it can 
be pressed in it is divisible. 

Moreover, no weight can consist of parts not possessing 15 
weight. For how, except by the merest fiction, can they 
specify the number and character of the parts which will 
produce weight ? And, further, when one weight is greater 
than another, the difference is a third weight ; from which 
it will follow that every indivisible part possesses weight. 
For suppose that a body of four points possesses weight. 
A body composed of more than four points^ will be 
superior in weight to it, a thing which has weight. But the 20 
difference between weight and weight must be a weight, as 
the difference between white and whiter is white. Here the 
difference which makes the superior weight heavier ^ is the 
single point which remains when the common number, four, 
is subtracted. A single point, therefore, has weight. 

Further, to assume, on the one hand, that the planes can 

^ Prantl's conjecture ^ tov8l is unsatisfactory. The alternatives are 
(i)_to keep the reading of the manuscripts (7 T08I.), (2) to read rovdi, 
omitting fj. In the latter case the sense remains the same but the 
construction becomes rather easier. 

^ Prantl's conjectural duplication of the words /zm crrtyfifj, though 
harmless, is unnecessary. 



299^ DE CAELO 

25 only be put in linear contact ^ would be ridiculous. For 
just as there are two ways of putting lines together, namely, 
end to end and side by side, so there must be two ways of 
putting planes together. Lines can be put together so that 
contact is linear by laying one along the other, though not 
by putting them end to end.^ But if, similarly, in putting 
the planes together, superficial contact is allowed as an 

30 alternative to linear, that method will give them bodies 
which are not any element nor composed of elements.^ 
Again, if it is the number of planes in a body ^ that makes 
300^ one heavier than another, as the Timaeus^ explains, 
clearly the line and the point will have weight. For the 
three cases are, as we said before, analogous.^ But if the 
reason of differences of weight is not this, but rather the 
5 heaviness of earth and the lightness of fire, then some of 
the planes will be light and others heavy (which involves 
a similar distinction in the lines and the points) ; the earth- 
plane, I mean, will be heavier than the fire-plane. In 
general, the result is either that there is no magnitude at 
all, or that all magnitude could be done away with. For 

TO a point is to a line as a line is to a plane and as a plane is 
to a body. Now the various forms in passing into one 
another will each be resolved into its ultimate constituents. 
It might happen therefore that nothing existed except 
points, and that there was no body at all. A further con- 
sideration is that if time is similarly constituted, there would 
be, or might be, a time at which it was done away with. For 

15 the indivisible now is like a point in a line. The same conse- 
quences follow from composing the heaven of numbers, as 
some of the Pythagoreans do who make all nature out of 
numbers. For natural bodies are manifestly endowed with 
weight and lightness, but an assemblage of units can neither 
be composed to form a body nor possess weight. 

^ i. e. so as to form pyramids, cubes, &c. 

^ Grammar requires the readings eTrirt^f/xeV?;, TrpocrTidefxevr) instead of 
the eTTiTLdejjLfvrjv, npoaTiOe^evrjv of all manuscripts but one (M). 

^ Because they will not be pyramids or instances of any other 
recognized figure. 

■* Omitting the rd before to)v (imrehwv, which got into E by a simple 
dittography and is found in no other manuscript. 

^ Plato, 'Jvn. 56 B. 

^ i.e. point : line :: line : plane :: plane : body (as below). 



BOOK III. 2 300^ 

2 The necessity that each of the simple bodies should have 20 
a natural movement may be shown as follows. They mani- 
festly move, and if they have no proper movement they 
must move by constraint : and the constrained is the same 
as the unnatural. Now an unnatural movement presupposes 
a natural movement which it contravenes, and which, how- 25 
ever many the unnatural movements, is always one. For 
naturally a thing moves in one way, while its unnatural 
movements are manifold.^ The same may be shown from 
the fact of rest. Rest, also, must either be constrained or 
natural, constrained in a place to which movement was con- 
strained, natural in a place movement to which was natural. 
Now manifestly there is a body which is at rest at the 30 
centre. If then this rest is natural to it, clearly motion to 
this place is natural to it. If, on the other hand, its rest 
is constrained, what is hindering its motion ? Something, 
perhaps, which is at rest : but if so, we shall simply repeat 
the same argument ; and either we shall come to an ultimate 
something to which rest where it is is natural, or we shall 300^ 
have an infinite process, which is impossible. The hindrance 
to its movement, then, we will suppose, is a moving thing — 
as Empedocles says that it is the vortex which keeps the 
earth still — : but in that case we ask, where would it have 
moved to but for the vortex P^ It could not move in- 
finitely ; for to traverse an infinite is impossible, and im- 5 
possibilities do not happen. So the moving thing must 
stop somewhere, and there rest not by constraint but 
naturally. But a natural rest proves a natural movement 

^ This is in verbal contradiction with the doctrine of Book I, which 
asserts that the unnatural movement is single since it is the contrary 
of the natural, which is single. But it is not difficult to conceive of 
all movements of a body divergent from the one natural path as 
unnatural according to the degree of their divergence, even though, 
strictly construed, the unnatural path is also one. 

^ This question, though relevant to the general problem, is not 
specially relevant to the hypothesis that the obstacle is in movement. 
There is therefore something to be said for an interpretation which, like 
that attributed by Simplicius to Alexander, makes the question refer 
to the supposed moving obstacle instead of to the earth. But 
Alexander's interpretation turns out on examination to create more 
difficulties than it removes : and there is no great objection, after all, 
to supposing that Aristotle refutes the second alternative by an argu- 
ment which refutes both. 

645.20 H 



3oo^ DE CAELO 

to the place of rest. Hence Leucippus and Democritus, 
who say that the primary bodies are in perpetual movement 

10 in the void or infinite, may be asked to explain the manner 
of their motion and the kind of movement which is natural 
to them. For if the various elements are constrained by 
one another to move as they do, each must still have 
a natural movement which the constrained contravenes, and 
the prime mover must cause motion not by constraint but 

15 naturally. If there is no ultimate natural cause of move- 
ment and each preceding term in the series is always moved 
by constraint, we shall have an infinite process. The same 
difficulty is involved even if it is supposed, as we read in 
the Tiinaetis} that before the ordered world was made the 
elements moved without order. Their movement must 
have been due either to constraint or to their nature. And 

20 if their movement was natural, a moment's consideration 
shows that there was already an ordered world. For the 
prime mover must cause motion in virtue of its own natural 
movement,^ and the other bodies, moving without constraint, 
as they came to rest in their proper places, would fall into 
the order in which they now stand, the heavy bodies moving 

25 towards the centre and the light bodies away from it. But 
that is the order of their distribution in our world. There 
is a further question, too, which might be asked. Is it pos- 
sible or impossible that bodies in unordered movement 
should combine in some cases into combinations like those 
of which bodies of nature's composing are composed, such, 
I mean, as bones and flesh ? Yet this is what Empedocles 

30 asserts to have occurred under Love. ' Many a head ', says 

' Plato, Tivi. 30 a, 

^ Taking the reading for which Alexander argued— xti^eii/ aWo kivov- 
fxevov Kara cf)vaiv. I should put a comma after Kivelv and take Kara (f). 
with Kivnvnevov. The hypothesis is that the elements have their 
natural movements ; and the dependent clause avro klv. k. (p. applies 
this hypothesis to the prime mover, as to Kwoiifxeva jxr) ^la applies it to 
the other bodies. Aristotle shows that, on this hypothesis, the present 
world-order would exist : the prime mover would be imparting move- 
ment to the bodies within it, as it does now, and the four elements 
would be moving towards or resting in their proper places, as now. 
If avTo'is read, we have a more disputable description of this Koafxos 
and less use for the words KLvovfxevov Kara (pvatv. avro is said to be 
the reading of the manuscripts, iDut neither copyists nor collators are 
to be trusted with a breathing. J has avro {sic). 



BOOK III. 2 300^ 

he, * came to birth without a neck.' ^ The answer to the 
view that there are infinite bodies moving in an infinite is 
that, if the cause of movement is single, they must move 
with a single motion, and therefore not without order ; and 
if, on the other hand, the causes are of infinite variety, their 301^ 
motions too must be infinitely varied. For a finite number 
of causes would produce a kind of order, since absence of 
order is not proved by diversity of direction in motions : 
indeed, in the world we know, not all bodies, but only 
bodies of the same kind, have a common goal of movement. 
Again, disorderly movement means in reality unnatural 5 
movement, since the order proper to perceptible things is 
their nature. And there is also absurdity and impossibility 
in the notion that the disorderly movement is infinitely con- 
tinued. For the nature of things is the nature which most 
of them possess for most of the time. Thus their view 
brings them into the contrary position^ that disorder is 10 
natural, and order or system unnatural. But no natural 
fact can originate in chance. This is a point which Anaxa- 
goras seems to have thoroughly grasped ; for he starts his 
cosmogony from unmoved things. The others, it is true, 
make things collect together somehow before they try to 
produce motion and separation. But there is no sense in 
starting generation from an original state in which bodies 15 
are separated and in movement. Hence Empedocles 
begins after the process ruled by Love : for he could not 
have constructed the heaven by building it up out of 
bodies in separation, making them to combine by the power 
of Love, since our world has its constituent elements in 
separation, and therefore presupposes a previous state of 
unity and combination.^ 20 

These arguments make it plain that every body has its 
natural movement, which is not constrained or contrary to 
its nature. We go on to show that there are certain bodies * 

^ Emped. fr. 57, 1. i (Diels, Vors.^ 245, 20). 

^ Reading o-vfxjiaLvei, with HMJ, for a-vfx^aivnv, 

^ Putting a comma instead of a full-stop after aToix^iav (1. 19). 

^ The proposition to be proved is that some bodies have fiecessarily 
this kind of impetus. The introduction of necessity shows that we are 
dealing with a universal. Below in 301^ 16, and again in 301^30, we 

H 2 



301^ DE CAELO 

whose necessary impetus is that of weight and lightness. 
Of necessity, we assert, they must move, and a moved thing 

25 which has no natural impetus cannot move either towards 
or away from the centre. Suppose a body A without weight, 
and a body B endowed with weight. Suppose the weight- 
less body to move the distance CD, while B in the same 
time moves the distance CE^ which will be greater since the 
heavy thing must move further. Let the heavy body then 

30 be divided in the proportion CE : CD (for there is no reason 
why a part of B should not stand in this relation to the 
whole). Now if the whole moves the whole distance CE, 
the part must in the same time move the distance CD. 
A weightless body, therefore, and one which has weight 
301^ will move the same distance, which is impossible. And 
the same argument would fit the case of lightness. Again, 
a body which is in motion but has neither weight nor light- 
ness, must be moved by constraint, and must continue its 
constrained movement infinitely. For there will be a force 
5 which moves it, and the smaller and lighter a body is the 
further will a given force move it. Now let A, the weight- 
less body, be moved the distance CE, and B, which has 
weight, be moved in the same time the distance CD. 
Dividing the heavy body in the proportion CE : CD, we 

10 subtract from the heavy body a part which will in the same 
time move the distance CE, since the whole moved CD : 
for the relative speeds of the two bodies will be in inverse 
ratio to their respective sizes. Thus the weightless body 
will move the same distance as the heavy in the same time. 

15 But this is impossible. Hence, since the motion of the 
weightless body will cover a greater distance than any that 
is suggested,^ it will continue infinitely. It is therefore 
obvious that every body must have a definite ^ weight or 

are told that e^'ery body is either hght or heavy. Aristotle's readers 
would of course understand that the disjunction only applied uni- 
versally 'beneath the moon'. The more cautious statement in this 
passage allows for the exception of the heavenly body. 

^ Reading nporedevTos, which is given by all manuscripts except M 
and by Simplicius. 

^ i.e. not infinite, bicopiayievov is here equivalent to lopia-p-ivov. 
A similar tendency is observable in other derivatives of bioplCuv, e.g. 
uhiopiaTos. Alexander and Simplicius made great, but not very 



BOOK III. 2 301^ 

lightness. But since ' nature ' means a source of movement 
within the thing itself, while a force is a source of move- 
ment in something other than it or in itself qua other/ and 
since movement is always due either to nature or to con- ao 
straint, movement which is natural, as downward movement 
is to a stone, will be merely accelerated by an external 
force, while an unnatural movement will be due to the force 
alone.^ In either case the air is as it were instrumental to 
the force. For air is both light and heavy, and thus qua 
light produces upward motion, being propelled and set in 
motion by the force, and qua heavy produces a downward 25 
motion. In either case the force transmits the movement 
to the body by first, as it were, impregnating the air." 
That is why a body moved by constraint continues to move 
when that which gave the impulse ceases to accompany it. 
Otherwise, i. e. if the air were not endowed with this func- 
tion, constrained movement would be impossible. And 
the natural movement of a body may be helped on in the 30 
same way. This discussion suffices to show* (i) that all 
bodies are either light or heavy, and (2) how unnatural 
movement takes place. 

From what has been said earlier ^ it is plain that there 

successful, efforts to interpret the word as qualifying 'body': they 
do not consider the possibility of its qualifying ^apo^ r) KovcpoTTjTa. 
Probably their manuscripts, like FHMJ, had to before dicopianei^ov, 
which would make it difificult or impossible to take dicopio-pepov in 
that way. 

^ Reading r) 77 aXKo. It looks as if Simplicius had this reading (see 
critical note to Heiberg's edition, p. 595, 22) : his interpretation 
requires it. 

^ Reading OdrTO) in 1. 20, with all manuscripts except F and with 
Simplicius. amr) in 22 is somewhat vague in reference, but must 
stand for r] Swa/uis avrrj. 

^ 11. 23-5, 7re(pvK€ . . . ^apvs, are grammatically a parenthesis, and 
should be so printed, with a colon in 23 after (Bapvs. For the doctrine 
cf. P/iys. IV. 8 and VIII. 10. 

* Simplicius and Alexander, with three of our manuscripts (FHAI), 
have eV tovtols for €k tovtodv. iv TovTOLs would go with exovo-t rather 
than with (pavepov, qualifying the application of the second clause. 
The qualification, however, cannot be made very precise, and it is 
best to follow the other three manuscripts. 

° The yap which introduces the next sentence shows that the 
justification of the statement is to come. The thesis follows from 
what was 'said earlier', because in Phys. IV. 6-9 the hypothesis of 
a void was investigated and refuted, and it is here shown that absolute 
generation, or generation of body out of not-body, requires a void. 



30i^ DE CAELO 

cannot be generation either of everything or in an absolute 
sense of anything. It is impossible that everything should 
302^ be generated, unless an extra-corporeal ^ void is possible. 
For, assuming generation, the place which is to be occupied 
by that which is coming to be, must have been previously 
occupied by void in which no body was.^ Now it is quite 
possible for one body to be generated out of another, air 
5 for instance out of fire, but in the absence of any pre- 
existing mass generation is impossible. That which is 
potentially a certain kind of body may, it is true, become 
such in actuality. But if the potential body was not already 
in actuality some other kind of body, the existence of an 
extra-corporeal void must be admitted. 

10 It remains to say what bodies are subject to generation, 3 
and why. Since in every case knowledge depends on what 
is primary, and the elements are the primary constituents 
of bodies, we must ask which of such bodies ^ are elements, 
and why ; and after that what is their number and character. 

15 The answer will be plain if we first explain what kind of 
substance an element is. An element, we take it, is a body 
into which other bodies may be analysed, present in them 
potentially or in actuality (which of these, is still disputable), 
and not itself divisible into bodies different in form. That, 
or something like it, is what all men in every case mean by 

20 element. Now if what we have described is an element, 
clearly there must be such bodies. For flesh and wood 
and all other similar bodies contain potentially fire and 
earth, since one sees these elements exuded from them ; 
and, on the other hand, neither in potentiality nor in actuality 

25 does fire contain flesh or wood, or it would exude them. 

The nature of the heavenly body and the views of Parmenides and 
MehssLis, referred to by Simphcius, are not here in point. 

* i.e. a void outside bodies, as distinct from the fragments of void 
which are supposed to be distributed throughout the texture of every 
body. Simplicius attributes the distinction of two kinds of void to the 
autliors of the theory themselves. 

^ Reading in h 2 to yivcfifvov, d iyevfro with Bekker. The manu- 
scripts are confused, and offer many variants. 

^ viz. bodies subject to generation. VVe read noln to>u ToiovTcau with 
the manuscripts, taking t6)u tokwtuv as a partitive genitive (after 
Simplicius). 



BOOK III. 3 302' 

Similarly, even if there were only one elementary body, 
it would not contain them. For though it will be either 
flesh or bone or something else, that does not at once 
show that it contained these in potentiality : the further 
question remains, in what manner it becomes them. Now 
Anaxagoras opposes Empedocles' view of the elements. 
Empedocles says that fire and earth and the related bodies 30 
are elementary bodies of which all things are composed ; 
but this Anaxagoras denies. His elements are the homoeo- 
merous things,^ viz. flesh, bone, and the like. Earth and 302^ 
fire are mixtures, composed of them and all the other seeds, 
each consisting of a collection of all the homoeomerous 
bodies, separately invisible ; and that explains why from 
these two bodies all others are generated. (To him fire 
and aither are the same thing.^) But since every natural 5 
body has its proper movement, and movements are either 
simple or mixed, mixed in mixed bodies and simple in 
simple, there must obviously be simple bodies ; for there 
are simple movements. It is plain, then, that there are 
elements, and why. 

4 The next question to consider is whether the elements 10 
are finite or infinite in number, and, if finite, what their 
number is. Let us first show reason for denying that 
their number is infinite, as some suppose. We begin with 
the view of Anaxagoras that all the homoeomerous bodies 
are elements.^ Any one who adopts this view misapprehends 15 
the meaning of element. Observation shows that eveamixed 
bodies are often divisible into homoeomerous parts ; examples 
are flesh, bone, wood, and stone. Since then the composite 

^ 'Homoeomerous' means 'having parts like one another and like 
the whole of which they are parts '. Some confusion is here caused 
by the fact that Aristotle sometimes uses ' homoeomerous * as an 
attribute of the parts of a homoeomerous whole, i. e. as meaning ' like 
one another and like the whole of which they are parts '. That is 
what he means when he says of a body (302^ 16) that it is ' divisible 
into homoeomerous parts' or {ib. 25) that it is 'composed of homoeo- 
merous bodies'. The use of the term XeTrro/iepe? {= ^ik pone pes) is 
complicated by a similar transference from whole to part (cp. 304^ 9, 
note). 

^ Cp. Book I, 270^24. 

^ rolls' . . . TTuiovvTas must be construed (by a kind of zeugma) with 
d€a)pr]Teou. 



302^ DE CAELO 

cannot be an element, not every homoeomerous body can 
be an element ; only, as we said before,^ that which is 

20 not divisible into bodies different in form.^ But even 
taking * element ' as they do, they need not assert an 
infinity of elements, since the hypothesis of a finite number 
will give identical results. Indeed even two or three such 
bodies serve the purpose as well, as Empedocles' attempt 
shows. Again, even on their view it turns out that all 

25 things are not composed of homoeomerous bodies. They 
do not pretend that a face is composed of faces, or that any 
other natural conformation is composed of parts like itself.^ 
Obviously then it would be better to assume a finite number 
of principles. They should, in fact, be as few as possible, 
consistently with proving what has to be proved. This is 

30 the common demand of mathematicians, who always assume 
as principles things finite either in kind or in number.* 
Again, if body is distinguished from body by the ap- 
propriate qualitative difference, and there is a limit to 
303^ the number of differences (for the difference lies in qualities 
apprehended by sense, which are in fact finite in number, 
though this requires proof ^), then manifestly there is neces- 
sarily a limit to the number of elements. 

There is, further, another view — that of Leucippus and 
Democritus of Abdera— the implications of which are also 

^ Above, 302^18. 

^ 'Divisible into homoeomerous parts ' = ' homoeomerous wholes' 
(cp. note on 'homoeomerous' at 302^31). The argument is therefore 
as follows : ' homoeomerous ' includes mixed as well as simple bodies ; 
but any one who understood the meaning of the term ' element ' would 
have seen that a mixed body cannot be an element : instead of 
regarding all homoeomerous bodies as elements, he would have 
confined the term to such homoeomerous bodies as are simple. — As 
an argument against Anaxagoras this is ineffective ; for he (a) denied 
that flesh, bone, &c., are mixed; (d) denied that earth, air, fire, and 
water — cited by Simplicius as simple and homoeomerous— are simple. 
Aristotle is content to argue from what he regards as estabhshed fact, 
whether Anaxagoras admits it or not. Anaxagoras would have 
claimed that the suggested criterion of indivisibility Kar eldos was 
satisfied by his ojioiofxepr}^ and could therefore plead not guilty to the 
charge of misapprehending the meaning of ' element '. 

•' All bodies should be either elements or composed of elements. 
But Anaxagoras, though he makes his elements infinite, is still not 
able to show that every whole is composed of parts like itself. 

* Reading ra Trenepaafxeva (so J, as well as three of Bekker's manu- 
scripts). 

•' The proof of the proposition is given in De Scnsic^ 6 (445'* 2off.). 



BOOK III. 4 303' 

unacceptable. The primary masses, according to them, 5 
are infinite in number and indivisible in mass : one cannot 
turn into many nor many into one; and all things are 
generated by their combination and involution. Now this 
view in a sense makes things out to be numbers or composed 
of numbers.^ The exposition is not clear, but this is its 10 
real meaning. And further, they say that since the atomic 
bodies differ in shape, and there is an infinity of shapes, 
there is an infinity of simple bodies. But they have never 
explained in detail the shapes of the various elements, 
except so far as to allot the sphere to fire. Air, water, 15 
and the rest they distinguished by the relative size of 
the atom, assuming that the atomic substance was a sort 
of master-seed for each and every element. Now, in 
the first place, they make the mistake already noticed. 
The principles which they assume are not limited in 
number, though such limitation would necessitate no other 
alteration in their theory. Further, if the differences of 
bodies are not infinite, plainly the elements will not be 20 
an infinity.^ Besides, a view which asserts atomic bodies 
must needs come into conflict with the mathematical 
sciences, in addition to invalidating many common opinions 
and apparent data of sense perception. But of these things 
we have already spoken in our discussion of time and move- 
ment.^ They are also bound to contradict themselves. 25 
For if the elements are atomic, air, earth, and water cannot 
be differentiated by the relative sizes of their atoms, since 
then they could not be generated out of one another. The 
extrusion of the largest atoms is a process that will in time 
exhaust the supply ; and it is by such a process that they 
account for the generation of water, air, and earth from one 
another.'* Again, even on their own presuppositions it does 30 

^ Because the atom is practically a mathematical unit, out of which 
bodies are formed by simple addition. Cp. Met. Z. 13, 1039^3 ff. 

'' Cp. 303a I. 3 £gp_ pj^y^^ YJ^ I_2 ^231^ 18 ff.). 

* Suppose water is being formed out of air; and suppose that the 
water-atom is larger than the air-atom: what is required on this 
theory is the extrusion from the air of the larger atoms. Conversely, 
if air were being formed out of water, the smaller atoms would be 
extruded from the water. But the supply of large (or small) atoms 
will soon run out, and air not reducible to water (or water not reducible 
to air) will be left. 



303^ DE CAELO 

not seem as if the elements would be infinite in number. 
The atoms differ in figure, and all figures are composed of 
303^ pyramids, rectilinear in the case of rectilinear figures, while 
the sphere has eight pyramidal parts.^ The figures must 
h^ve their principles,^ and, whether these are one or two 
or more, the simple bodies must be the same in number 
as they. Again, if every element has its proper movement, 
5 and a simple body has a simple movement, and the number 
of simple movements is not infinite, because the simple 
motions are only two and the number of places is not 
infinite,^ on these grounds also we should have to deny 
that the number of elements is infinite. 

Since the number of the elements must be limited, it 5 
ro remains to inquire whether there is more than one element. 
Some assume one only, which is according to some ^ water, 
to others ^ air, to others ^ fire, to others ^ again something 
finer than water and denser than air, an infinite body — 
so they say — embracing all the heavens. 

Now those who decide for a single element, which is 
either water or air or a body finer than water and denser 
^5 than air, and proceed to generate other things out of it 
by use of the attributes density and rarity, all alike fail 
to observe the fact that they are depriving the element 
of its priority. Generation out of the elements is, as they 
say, synthesis, and generation into the elem.ents is analysis, 

^ The pyramids are tetrahedrons; and those produced by triple 
section of a sphere are irregular, having a spherical base. 

"^ i. e. there must be a limited number of primary figures to which all 
other figures are reducible. 

^ There are only two places to which movement can be directed, 
viz. the circumference and the centre. By the two simple motions 
Aristotle probably here means motions towards these two places, 
motion up and motion down. Circular motion is not possible beneath 
the moon. 

* Thales and Hippon. 

° Anaximenes and Diogenes of Apollonia. 

^ Heracleitus and Hippasus : but see below, 304=^ 18, note. 

"^ Anaximander. This identification has been rejected by many 
modern scholars. See Bonitz, htd. 50^*33, Diels, Vof's."^ 18, 10 and 
416, I, Burnet, E.G.P.^ § 15. Diels follows Zeller in attributing the 
view to a certain Idaios of Himera, whom Aristotle never mentions 
by name and of whom hardly anything is known. Burnet refers the 
passage to Anaximander. 



BOOK III. 5 303^ 

so that the body with the finer parts must have priority 
in the order of nature. But they say that fire is of all 20 
bodies the finest. Hence fire will be first in the natural 
order. And whether the finest body is fire or not makes 
no difference ; anyhow it must be one of the other bodies 
that is primary and not that which is intermediate.^ Again, 
density and rarity, as instruments of generation, are equiva- 
lent to fineness and coarseness, since the fine is rare, and 
coarse in their use means dense. But fineness and coarse- 25 
ness, again, are equivalent to greatness and smallness, since 
a thing with small parts is fine and a thing with large parts 
coarse. For that which spreads itself out widely is fine, 
and a thing composed of small parts is so spread out. In 
the end, then, they distinguish the various other substances 
from the element by the greatness and smallness of their 3° 
parts. This method of distinction makes all judgement rela- 
tive. There will be no absolute distinction between fire, water, 
and air, but one and the same body will be relatively to 
this fire, relatively to something else air.^ The same 3^4^ 
difficulty is involved equally in the view which recognizes 
several elements and distinguishes them by their greatness 
and smallness. The principle of distinction between bodies 
being quantity, the various sizes will be in a definite ratio, 
and whatever bodies are in this ratio to one another must be 5 
air, fire, earth, and w^ater respectively. For the ratios of 
smaller bodies may be repeated. among greater bodies.^ 

Those who start from fire as the single element, while 
avoiding this difficulty, involve themselves in many others. 
Some of them give fire a particular shape, like those who 10 
make it a pyramid, and this on one of two grounds. The 
reason given may be — more crudely — that the pyramid is 
the most piercing of figures as fire is of bodies,"^ or — more 

^ i. e. the rarest or finest body is the true element, as being the true 
starting-point of the process of generation or synthesis ; and a body 
denser than fire and rarer than earth, like air or water, or finer than 
water and denser than air, like Anaximander's infinite, will not do. 

^ For the attributes great and small belong to the category of 
relation (G?/. 5^ 10 fT.). 

^ i. e. what is really asserted is a ratio, and ratio is independent 
of size. 

* Simplicius observes that the argument is justly called crude, since 



304^ DE CAELO 

ingeniously — the position may be supported by the follow- 
ing argument. As all bodies are composed of that which 

T5 has the finest parts, so all solid figures are composed of 
pyramids : but the finest body is fire, while among figures 
the pyramid is primary and has the smallest parts ; ^ and 
the primary body must have the primary figure : therefore 
fire will be a pyramid.^ Others, again, express no opinion on 
the subject of its figure, but simply regard it as the body 

20 of the finest parts, which in combination will form other 
bodies, as the fusing of gold-dust produces solid gold. 
Both of these views involve the same difficulties. For (i) 
if, on the one hand, they make the primary body an atom, 
the view will be open to the objections already advanced 
against the atomic theory. And further the theory is incon- 

25 sistent with a regard for the facts of nature. For if all 
bodies are quantitatively commensurable, and the relative 
size of the various homoeomerous masses and of their 
several elements are in the same ratio, so that the total 
mass of water,^ for instance, is related to the total mass 
of air as the elements of each are to one another, and 

30 so on, and if there is more air than water and, generally, 
more of the finer body than of the coarser, obviously the 
element of water will be smaller than that of air.* But 
the lesser quantity is contained in the greater. Therefore 



it involves an undistributed middle : 'fire is piercing', 'the pyramid 
is piercing': they attempt to draw an affirmative conclusion in the 
second figure. 

^ Reading ^iKpojxepia-raTov with FHMJ. The word is used as 
equivalent to XeTTTo^epeo-raTov, which is the reading of EL and (prob- 
ably) of Simplicius. — The pyramid is presumably said to have the 
smallest parts because it contains fewer of the primary triangles than 
any other regular solid. But the assertion is not thereby justified. 
Given a certain size of triangle, the pyramid would be the smallest of 
the solids in cubic content ; thus the body composed of pyramids 
would be the body with the smallest parts. The epithet XeTrro/xepeV, 
in short, seems to be transferred from the whole to the part, just as 
ofjioionepes was (above, 302'' 3 1, note). 

2 To whom is this ' more ingenious ' version to be attributed ? 
' Heracleitus made fire the universal element but did not say it was 
a pyramid, and the Pythagoreans, who said that fire was composed 
of pyramids, did not make it the universal element' (Simpl.). 

^ Perhaps olop to should be read for olov ra. 

* The ascertained fact on which this argument is based is that 
when (e.g.) water turns into air, the volume of the resultant air is 



BOOK III. 5 304^ 

the air element is divisible. And the same could be shown 304*^ 
of fire and of all bodies whose parts are relatively fine. 
(2) If, on the other hand, the primary body is divisible, then 
(a) those who give fire a special shape will have to say 
that a part of fire is not fire, because a pyramid is not 
composed of pyramids,^ and also that not every body 5 
is either an element or composed of elements, since a 
part of fire will be neither fire nor any other element. 
And (3) those whose ground of distinction is size will 
have to recognize an element prior to the element, a 
regress which continues infinitely, since every body is di- 
visible and that which has the smallest parts is the element.^ 
Further, they too will have to say that the same body is 
relatively to this fire and relatively to that air, to others 10 
again water and earth. 

The common error of all views which assume a single 
element is that they allow only one natural movement, 
which is the same for every body. For it is a matter 
of observation that a natural body possesses a principle 
of movement. If then all bodies are one. all will have 15 
one movement. With this motion the greater their quantity 
the more they will move, just as fire, in proportion as its 
quantity is greater, moves faster with the upward motion 
which belongs to it. But the fact is that increase of quantity 
makes many things move the faster downward. For these 
reasons, then, as well as from the distinction already 20 
established^ of a plurality of natural movements, it is 
impossible that there should be only one element. But 
if the elements are not an infinity and not reducible to 
one, they must be several and finite in number. 

greater than that of the original water. This increase of volume can 
only be accounted for (since the hypothesis of a void has been refuted) 
by supposing an increase in the volume of the atom proportionate to 
the observed increase in the volume of the total mass. But the 
enlarged atom would be divisible, and therefore no atom. 

' i. e. a pyramid cannot be divided so that every part is a pyramid. 

^ If every body is infinitely divisible, it is difficult to give a precise 
meaning to ' that which has the smallest parts '. Further, the phrase, 
as used, is somewhat illogical ; for the argument would point to the 
smallest part of any body, rather than the body with the smallest 
parts, as the element. But the use of XeTrro/xepef (and fxiKpoixepes) as 
an epithet of the part instead of the whole occurs elsewhere (cf note 
on 304a 16). 3 gQQ^ j^ ^^ ij_ 



304^ DE CAELO 

First we must inquire whether the elements are eternal 6 
or subject to generation and destruction ; for when this 

25 question has been answered their number and character will 
be manifest. In the first place, they cannot be eternal. 
It is a matter of observation that fire, water, and every 
simple body undergo a process of analysis, which must ^ 
either continue infinitely or stop somewhere, (i) Suppose 
it infinite. Then the time occupied by the process will be 
infinite, and also that occupied by the reverse process of 

30 synthesis. For the processes of analysis and synthesis 
succeed one another in the various parts. It will follow 
that there are two infinite times which are mutually exclu- 
sive, the time occupied by the synthesis, which is infinite, 
being preceded by the period of analysis. There are thus 
305^ two mutually exclusive infinites, which is impossible. 
(2) Suppose, on the other hand, that the analysis stops 
somewhere. Then the body at which it stops will be either 
atomic or, as Empedocles seems to have intended, a divisible 
body which will yet never be divided. The foregoing argu- 
5 ments ^ show that it cannot be an atom ; but neither can it 
be a divisible body which analysis will never reach. For 
a smaller body is more easily destroyed than a larger ; 
and a destructive process which succeeds in destroying, 
that is, in resolving into smaller bodies, a body of some 
size, cannot reasonably be expected to fail with the smaller 

10 body. Now in fire we observe a destruction of two kinds : 
it is destroyed by its contrary when it is quenched, and 
by itself when it dies out.^ But the effect is produced by 
a greater quantity upon a lesser, and the more quickly the 
smaller it is. The elements of bodies must therefore be 
subject to destruction and generation. 

Since they are generated, they must be generated either 

15 from something incorporeal or from a body, and if from 
a body, either from one another or from something else. 
The theory which generates them from something in- 



^ Reading amiyKr] de with the MSS. ^ c. iv. 

•"' i.e. it may die out 'of itself . Aristotle does not develop this, but 
his point is only the simple one that the smaller the fire is, the sooner, 
by either process, it is destroyed. 



BOOK III. 6 305^ 

corporeal requires an extra-corporeal void.^ For every- 
thing that comes to be comes to be in something,^ and that 
in which the generation takes place must either be in- 
corporeal or possess body ; and if it has body, there will be 
two bodies in the same place at the same time, viz. that 
which is coming to be and that which was previously there, 20 
while if it is incorporeal, there must be an extra-corporeal 
void. But we have already shown ^ that this is impossible. 
But, on the other hand, it is equally impossible that the 
elements should be generated from some kind of body. 
That would involve a body distinct from the elements and 
prior to them. But if this body possesses weight or light- 
ness, it will be one of the elements ; and if it has no 25 
tendency to movement, it will be an immovable or mathe- 
matical entity, and therefore not in a place at all. A place 
in which a thing is at rest is a place in which it might move, 
either by constraint, i. e. unnaturally, or in the absence of 
constraint, i. e. naturally. If, then, it is in a place and 
somewhere,^ it will be one of the elements; and if it is 
not in a place, nothing can come from it, since that which 3o 
comes into being and that out of which it comes must 
needs be together. The elements therefore cannot be 
generated from something incorporeal nor from a body 
which is not an element, and the only remaining alternative 
is that they are generated from one another. 

7 We must, therefore, turn to the question, what is the 
manner of their generation from one another? Is it as 
Empedocles and Democritus say, or as those who resolve 35 
bodies into planes say, or is there yet another possibility? 3^5^ 

^ yevva>fX€vov is found only in EL, and the other four manuscripts 
offer no substitute. It was clearly not in Simplicius' text. Kexoopio-fxevou, 
or another word of similar meaning, must be read. 

'^ The words ev nvi ytvfrni Kai are a conjectural addition suggested 
by Simplicius (after Alexander). They occur (without the Kni) in one 
of our manuscripts, M, whose original readings are mostly either 
errors or conjectures. Without these words it is almost impossible 
to make any sense of the passage ; but they are not intrinsically 
a probable conjecture and are only accepted because a better remedy 
remains to be suggested. 

3 Phys. IV. 8. 

^ Placing the comma after nov (1 29) instead of after toVo) (1. 28). 
To be ' somewhere ' is to be ' in a place '. 



305^ DE CAELO 

(i) What the followers of Empedocles do, though without 
observing it themselves, is to reduce the generation of 
elements out of one another to an illusion. They make it 
a process of excretion from a body of what was in it all the 
time — as though generation required a vessel rather than 
5 a material — so that it involves no change of anything. 
And even if this were accepted, there are other implications 
equally unsatisfactory. We do not expect a mass of matter 
to be made heavier by compression. But they will be 
bound to maintain this, if they say that water is a body 
present in air and excreted from air, since air becomes 

lo heavier when it turns into water.^ Again, when the mixed 
body is divided, they can show no reason why one of the 
constituents must by itself take up more room than the 
body did : but when water turns into air, the room occu- 
pied is increased. The fact is that the finer body takes 
up more room, as is obvious in any case of transforma- 

15 tion. As the liquid is converted into vapour or air the 
vessel which contains it is often burst because it does not 
contain room enough. Now, if there is no void at all, and 
if, as those who take this view say, there is no expansion of 
bodies,^ the impossibility of this is manifest : and if there 
is void and expansion, there is no accounting for the fact 
that the body which results from division occupies of 

20 necessity a greater space. It is inevitable, too, that genera- 
tion of one out of another should come to a stop, since a 
finite quantum cannot contain an infinity of finite quanta. 
When earth produces water something is taken away from 
the earth, for the process is one of excretion. The same 
thing happens again when the residue produces water. 

25 But this can only go on for ever, if the finite body con- 
tains an infinity, which is impossible. Therefore the 
generation of elements out of one another will not always 
continue.^ 

' More accurately, becomes heavy, since air rises and water falls. 
Lightness is treated here as a low degree of heaviness. 

^ The words Kddnnep (f)na\v ol r. X. must be taken to refer only to 
expansionj since Democritus of course believed in a void. 

^ In the end the elements will be sorted out, and there will remain 
several homogeneous masses between which no interchange is 
possible. 



BOOK III. 7 305 



(2) We have now explained that the mutual transforma- 
tions of the elements cannot take place by means of ex- 
cretion. The remaining alternative is that they should be 
generated by changing into one another. And this in one of 
two ways, either by change of shape, as the same wax takes 30 
the shape both of a sphere and of a cube, or, as some assert, 
by resolution into planes, (a) Generation by change of 
shape would necessarily involve the assertion of atomic 
bodies. For if the particles were divisible there would be a 
part of fire which was not fire and a part of earth which 
was not earth_, for the reason that not every part of a 35 
pyramid is a pyramid nor of a cube a cube. But if 306^ 
(b) the process is resolution into planes, the first difficulty 
is that the elements cannot all be generated out of one 
another. This they are obliged to assert, and do assert. It 
is absurd, because it is unreasonable that one element alone 
should have no part in the transformations, and also con- 
trary to the observed data of sense, according to which all 5 
alike change into one another. In fact their explanation of 
the observations is not consistent with the observations. 
And the reason is that their ultimate principles are wrongly 
assumed : they had certain predetermined views, and were 
resolved to bring everything into line with them. It seems 
that perceptible things require perceptible principles, 10 
eternal things eternal principles, corruptible things cor- 
ruptible principles ; and, in general, every subject matter 
principles homogeneous with itself. But they, owing to 
their love for their principles, fall into the attitude of men 
who undertake the defence of a position in argument. 
In the confidence that the principles are true Ihey are 
ready to accept any consequence of their application. 
As though some principles did not require to be judged 15 
from their results, and particularly from their final issue ! 
And that issue, which in the case of productive knowledge ^ 
is the product, in the knowledge of nature is the unim- 
peachable evidence of the senses as to each fact. 

The result of their view is that earth has the best right to 
the name element, and is alone indestructible ; for that 

^ i. e. in the case of art. 

645.20 I 



307^ DE CAELO 

not, however, well adapted to the movement of fire, which 
is an upward and rectilinear movement, but rather to that 
form of circular movement which we call rolling. Earth, 
again,^ they call a cube because it is stable and at rest. 
But it rests only in its own place, not anywhere ; from 

10 any other it moves if nothing hinders, and fire and the 
other bodies do the same. The obvious inference, there- 
fore, is that fire and each several element is in a foreign 
place a sphere or a pyramid, but in its own a cube. 
Again, if the possession of angles makes a body produce 

15 heat and combustion, every element produces heat, though 
one may do so more than another. For they all possess 
angles, the octahedron and dodecahedron as well as the 
pyramid ; and Democritus makes even the sphere a kind 
of angle, which cuts things because of its mobility.^ The 
difference, then, will be one of degree : and this is plainly 
false. They must also accept the inference that the mathe- 

2c matical solids produce heat and combustion, since they too 
possess angles and contain atomic spheres ^ and pyramids, 
especially if there are, as they allege, atomic figures.^ Any- 
how if these functions belong to some of these things and 
not to others, they should explain the difference, instead 
of speaking in quite general terms as they do. Again, 

25 combustion of a body produces fire, and fire is a sphere 
or a pyramid. The body, then, is turned into spheres or 
pyramids. Let us grant that these figures may reasonably 
be supposed to cut and break up bodies as fire does ; still 
it remains quite inexplicable that a pyramid must needs 
produce pyramids or a sphere spheres. One might as well 

30 postulate that a knife or a saw divides things into knives 
or saws. It is also ridiculous to think only of division 
when allotting fire its shape. Fire is generally thought 
of as combining and connecting rather than as separating. 

' Prantl has nnfLr'' for eVeir' by a misprint. 

^ Though it has a low degree of angularity, it is highly mobile and 
therefore extremely piercing. But the double cos is awkward, and 
perhaps the tradition is at fault. (J has refivn w? evKivr^Tou, supporting 
E against the other MSS.) 

" Prantl's acfimim is a misprint for a(f)nlpai. 

* i.e. indivisible units of line, of which the geometrical figures are 
composed. 



BOOK III. 8 307^ 

For though it separates bodies different in kind, it combines 307'' 
those which are the same ; and the combining is essential 
to it, the functions of connecting and uniting being a mark 
of fire, while the separating is incidental. For the expulsion 
of the foreign body is an incident in the compacting of the 
homogeneous. In choosing the shape, then, they should 
have thought either of both functions or preferably of the 5 
combining function. In addition, since hot and cold are 
contrary powers, it is impossible to allot any shape to 
the cold. For the shape given must be the contrary of that 
given to the hot, but there is no contrariety between 
figures. That is why they have all left the cold out, 
though properly either all or none should have their dis- 10 
tinguishing figures. Some of them, however, do attempt 
to explain this power, and they contradict themselves. 
A body of large particles, they say, is cold because instead 
of penetrating through the passages it crushes. Clearly, 
then, that which is hot is that which penetrates these 
passages, or in other words that which has fine particles. 
It results that hot and cold are distinguished not by the 15 
figure but by the size of the particles. Again, if the 
pyramids are unequal in size, the large ones will not be 
fire, and that figure will produce not combustion but its 
contrary. 

From what has been said it is clear that the difference 
of the elements does not depend upon their shape. Now 
their most important differences are those of property, 20 
function, and power ; for every natural body has, we main- 
tain, its own functions, properties, and powers. Our first 
business, then, will be to speak of these, and that inquiry 
will enable us to explain the differences of each from each. 



BOOK IV 

307^ We have now to consider the terms * heavy ' and * light *. I 
We must ask what the bodies so called are, how they are 
30 constituted, and what is the reason of their possessing these 
powers. The consideration of these questions is a proper 
part of the theory of movement, since we call things heavy 
and light because they have the power of being moved 
naturally in a certain way. The activities corresponding 
to these powers have not been given any name, unless 

308^ it is thought that ' impetus ' is such a name. But because 
the inquiry into nature is concerned with movement,^ and 
these things have in themselves some spark (as it were) 
of movement, all inquirers avail themselves of these powers, 
though in all but a few cases without exact discrimination. 
5 We must then first look at whatever others have said, and 
formulate the questions which require settlement in the 
interests of this inquiry, before we go on to state our own 
view of the matter. 

Language recognizes (a) an absolute, (5) a relative heavy 
and light. Of two heavy things, such as wood and bronze, 
we say that the one is relatively light, the other relatively 
10 heavy. Our predecessors have not dealt at all with the 
absolute use of the terms, but only with the relative. I mean, 
they do not explain what the heavy is or what the light 
is, but only the relative heaviness and lightness of things 
possessing weight. This can be made clearer as follows. 
There are things whose constant nature it is to move away 
15 from the centre, while others move constantly towards the 
centre ; and of these movements that which is away from 
the centre I call upward movement and that which is 
towards it I call downward movement. (The view, urged 
by some,^ that there is no up and no down in the heaven, 
is absurd. There can be, they say, no up and no down, since 

^ Read <pvaiKr)v fiiv ejvai (E alone omits /xev). 

'^ The digression is directed against Plato, Tim. 62 E ; but the view 
was held by others besides Timaeus. 



BOOK IV. I 308^ 

the universe is similar every way, and from any point on 20 
the earth's surface a man by advancing far enough will 
come to stand foot to foot with himself. But the extremity 
of the whole, which we call ' above ', is in position above and 
in nature primary. And since the universe has an extremity 
and a centre, it must clearly have an up and down. Common 
usage is thus correct,^ though inadequate. And the reason 25 
of its inadequacy is that men think that the universe is not 
similar every way. They recognize only the hemisphere 
which is over us. But if they went on to think of the 
world as formed on this pattern all round, with a centre 
identically related to each point on the extremity, they 
would have to admit that the extremity was above and 
the centre below.) By absolutely light, then, we mean that 
which moves upward or to the extremity, and by absolutely 3° 
heavy that which moves downward or to the centre. By 
lighter or relatively light we mean that one, of two bodies 
endowed with weight and equal in bulk, which is exceeded 
by the other in the speed of its natural downward move- 
ment.- 

2 Those of our predecessors who have entered upon this 
inquiry have for the most part spoken of light and heavy 35 
things only in the sense in which one of two things both 308^ 
endowed with weight is saidHo be the lighter. /\nd this 
treatment they consider a sufficient analysis also of the 
notions of absolute heaviness and absolute lightness, to 
which their account does not apply. This, however, will 
become clearer as we advance. One use of the terms 
' lighter ' and ' heavier ' is that which is set forth in writing 5 
in the Timaetis^ that the body which is composed of the 
greater number of identical parts is relatively heavy, while 
that which is composed of a smaller number is relatively 

^ Read ao-Trep with FHMJ. 

^ Accepting Prantl's first correction, ol (for o), which seems to be 
necessary to ihe sense. His second correction, "idoiv (for "urov), is to 
be rejected as unnecessary. Bywater (/. of Phil, xxviii, p. 242) 
suggests Oarepov, keeping o and 'iaov ; but the phrase, so emended, 
seems to be descriptive of the heavy rather than of the light. 

' 63 c. 



308^ DE CAELO 

light. As a larger quantity of lead or of bronze is heavier 
than a smaller — and this holds good of all homogeneous 
masses, the superior weight always depending upon a 

10 numerical superiority of equal parts — in precisely the same 
way, they assert, lead is heavier than wood.^ For all 
bodies, in spite of the general opinion to the contrary, are 
composed of identical parts and of a single material. But 
this analysis says nothing of the absolutely heavy and light. 
The facts are that fire is always light and moves upward, 
while earth and all earthy things move downwards or 

15 towards the centre. It cannot then be the fewness of the 
triangles (of which, in their view, all these bodies are com- 
posed) ^ which disposes fire to move upward. If it were, 
the greater the quantity of fire the slower it would move, 
owing to the increase of weight due to the increased 
number of triangles. But the palpable fact, on the contrary, 
is that the greater the quantity, the lighter the mass is and 

20 the quicker its upward movement : and, similarly, in the 
reverse movement from above downward, the small mass 
will move quicker and the large slower. Further, since to 
be lighter is to have fewer of these homogeneous parts and 
to be heavier is to have more, and air, water, and fire are 
composed of the same triangles, the only difference being 

25 in the number of such parts, which must therefore explain 
any distinction of relatively light and heavy between these 
bodies, it follows that there must be a certain quantum of 
air which is heavier than water. But the facts are directly 
opposed to this. The larger the quantity of air the more 
readily it moves upward, and any portion of air without 
exception will rise up out of the water. 

So much for one view of the distinction between light 

30 and heavy. To others '^ the analysis seems insufficient ; and 
their views on the subject, though they belong to an older 
generation than ours, have an air of novelty. It is apparent 

' I put a colon in 1. 6 after (XarTovcov and mark 11. 8-9, 6fxoi(os 5e . . . 
ea-Tiv, as parenthetical. This leaves an asyndeton at coanep in 1. 7, 
but it seems to give the sequence of thought better than the stopping 
of liekker and Prantl does. 

'^ There should be a comma after rpiyMPoiu in 1. 1 5. 

^ The atomists, Democritus and Leucippus. 



BOOK IV. 2 308'' 

that there are bodies which, when smaller in bulk than 
others, yet exceed them in weight. It is therefore obviously 
insufficient to say that bodies of equal weight are composed 
of an equal number of primary parts : for that would give 35 
equality of bulk. Those who maintain that the primary or 
atomic parts, of which bodies endowed with weight are 
composed, are planes, cannot so speak without absurdity; ^ 309' 
but those who regard them as solids are in a better position 
to assert that of such bodies the larger is the heavier. But 
since in composite bodies the weight obviously does not 
correspond in this way to the bulk, the lesser bulk being 
often superior in weight (as, for instance, if one be wool 5 
and the other bronze), there are some who think and say 
that the cause is to be found elsewhere. The void, they 
say, which is imprisoned in bodies, lightens them and 
sometimes makes the larger body the lighter. The reason 
is that there is more void. And this would also account for 
the fact that a body composed of a number of solid parts 
equal to, or even smaller than, that of another is sometimes 
larger in bulk than it. In short, generally and in every ^° 
case a body is relatively light when it contains a relatively 
large amount of void. This is the way they put it them- 
selves, but their account requires an addition. Relative 
lightness must depend not only on an excess of void, but 
also on a defect of solid : for if the ratio of solid to void 
exceeds a certain proportion, the relative lightness will ^5 
disappear. Thus fire, they say, is the lightest of things just 
for this reason that it has the most void. But it would 
follow that a large mass of gold, as containing more void 
than a small mass of fire, is lighter than it, unless it also 
contains many times as much solid. The addition is there- 
fore necessary. 

Of those who deny the existence of a void some, like 
Anaxagoras and Empedocles, have not tried to analyse the 
notions of light and heavy at all ; and those who, while still 20 
denying the existence of a void, have attempted this,^ have 

^ For, since the planes have no weight, their number cannot affect 
the weight of a body. 
"^ Plato, in the Timaeus. 



309^ DE CAELO 

failed to explain why there are bodies which are absolutely 
heavy and light, or in other words why some move upward 
and others downward. The fact, again, that the body of 

25 greater bulk is sometimes lighter than smaller bodies is one 
which they have passed over in silence, and what they have 
said gives no obvious suggestion for reconciling their views 
with the observed facts. 

But those who attribute the lightness of fire to its con- 
taining so much void are necessarily involved in practically 
the same difficulties. For though fire be supposed to 

30 contain less solid than any other body, as well as more 
void, yet there will be a certain quantum of fire in which 
the amount of solid or plenum is in excess of the solids 
contained in some small quantity of earth. They may 
reply that there is an excess of void also. But the question 
is, how will they discriminate the absolutely heavy ? Pre- 
sumably, either by its excess of solid or by its defect 
309^ of void. On the former view there could be an amount of 
earth so small as to contain less solid than a large mass of 
fire. And similarly, if the distinction rests on the amount 
of void, there will be a body, lighter than the absolutely 
light, which nevertheless moves downward as constantly as 
5 the other moves upward. But that cannot be so, since the 
absolutely light is always lighter than bodies which have 
weight and move downward, while, on the other hand, that 
which is lighter need not be light, because in common 
speech we distinguish a lighter and a heavier (viz. water 
and earth) among bodies endowed with weight. Again, 
the suggestion of a certain ratio between the void and the 
solid in a body is no more equal to solving the problem 

10 before us. This manner of speaking will issue in a similar 
impossibility. For any two portions of fire, small or great, 
will exhibit the same ratio of solid to void ; but the upward 
movement of the greater is quicker than that of the less, 
just as the downward movement of a mass of gold or lead, 

15 or of any other body endowed with weight, is quicker in 
proportion to its size. This, however, should not be the 
case if the ratio is the ground of distinction between heavy 
things and light. There is also an absurdity in attributing 



BOOK IV. 2 309^ 

the upward movement of bodies to a void which does not 
itself move. If, however, it is the nature of a void to move 
upward and of a plenum to move downward, and therefore 
each causes a like movement in other things,^ there was 20 
no need to raise the question why composite bodies are 
some light and some heavy ; they had only to explain why 
these two things are themselves light and heavy respectively, 
and to give, further, the reason why the plenum and the 
void are not eternally separated. It is also unreasonable 
to imagine a place for the void, as if the void were not 25 
itself a kind of place. ^ But if the void is to move, it must 
have a place out of which and into which the change carries 
it. Also what is the cause of its movement? Not, surely, 
its voidness : for it is not the void only which is moved, but 
also the solid.^ 

Similar difficulties are involved in all other methods of 
distinction, whether they account for the relative lightness 3° 
and heaviness of bodies by distinctions of size, or proceed 
on any other principle, so long as they attribute to each the 
same matter, or even if they recognize more than one 
matter, so long as that means only a pair of contraries. 
If there is a single matter, as with those who compose 
things of triangles, nothing can be absolutely heavy or light : 
and if there is one matter and its contrary — the void, for 3^0^ 
instance, and the plenum — no reason can be given for the 
relative lightness and heaviness of the bodies intermediate 
between the absolutely light and heavy when compared 
either with one another or with these themselves.* The 

^ Read (jiopas iKaripas. eKarepas is in all MSS. except E, and is 
implied in Simplicius' paraphrase. 

^ Read avTo with FHMJ and the corrector of E. The construction 
is certainly loose, but the other reading (avra) does not give the 
required sense. To give void a motion is to give it a ' place ', i. e. 
a natural place to which it moves. But it is itself nothing but a place 
where no body is (cf. P/iys. IV. 7) : and, as Simplicius punningly 
remarks, * it is out of place to give a place a place ' {tov 8e tottov totvov 

TToielv Ta>u droTrcorarcoi' eVriV). 

^ If movement is natural to both void and solid, the cause of move- 
ment must lie in something common to both and not in the peculiar 
nature of either, i. e. not in voidness or solidity. 

* Aristotle's argument is that the observed diversity of movement 
necessarily involves a corresponding diversity of bodies : hence any 
view which makes the four elements one in substance fails to account 



3io^ DE CAELO 

view which bases the distinction upon differences of size is 
5 more Hke a mere fiction than those previously mentioned, 
but, in that it is able to make distinctions between the four 
elements, it is in a stronger position for meeting the fore- 
going difficulties. Since, however,^ it imagines that these 
bodies which differ in size are all made of one substance, 
it implies, equally with the view that there is but one 
matter, that there is nothing absolutely light and nothing 
lo which moves upward (except as being passed by other 
things or forced up by them) ; ^ and since a multitude of 
small atoms are heavier than a few large ones, it will follow 
that much air or fire is heavier than a little water or earth, 
which is impossible. 

These, then, are the views which have been advanced by 3 
15 others and the terms in which they state them. We may 
begin our own statement by settling a question which to 
some has been the main difficulty — the question why some 
bodies move always and naturally upward and others down- 
ward, while others again move both upward and downward. 
After that we will inquire into light and heavy and the 
20 explanation of the various phenomena connected with 
them.'^ The local movement of each body into its own 
place must be regarded as similar to what happens in con- 
nexion with other forms of generation and change. There 

for the facts of movement. He here adds that it is not enough to 
recognize two kinds of substance or two contrary attributes. For 
there are four bodies to be accounted for. A single pair of opposites 
may yield an account of fire and earth, but they cannot account also 
for the ' intermediate bodies ', water and air. Two pairs of opposites 
will be required, such as those which he uses himself (warm, cold : 
dry, moist). — In 1. 3 Ta>v dnXc^v must refer to the things also called tcju 
unXSis ^ufjcav Koi Kov(^(iiv. Simplicius tells us that Alexander read 
Toiv anXwu, but found in some MSS. run/ (ittXcos. anXcos is tempting, 
but iniKuiv may be allowed to stand : for {a) the absolutely heavy and 
light are, on the theory criticized, pure solid and pure void respec- 
tively : thus TCI dTrXwf are ra dnXa : (d) all other bodies whatever will 
be composed of these in combination, and may therefore be opposed 
to them as composite to simple. 

^ Reading rw with HMLJ. Simplicius* paraphrase supports this. 

^ i.e. upward movement is either (a) illusory: as all things race 
downward, some, moving slower, are left behind, and thus appear to 
move up : or (d) unnatural : due to pressure applied from without by 
other bodies pushing downward. 

^ Prantl misprints yeVfrui for yivtrai. 



BOOK IV. 3 310' 

are, in fact, three kinds of movement, affecting respectively 
the size, the form, and the place of a thing, and in each it 
is observable that change proceeds from a contrary to 25 
a contrary or to something intermediate : it is never the 
change of any chance subject in any chance direction, nor, 
similarly, is the relation of the mover to its object for- 
tuitous : the thing altered is different from the thing 
increased, and precisely the same difference holds between 
that which produces alteration and that which produces 
increase. In the same manner it must be thought that 30 
that which produces local motion and that which is so 
moved are not fortuitously related. Now/ that which pro- 
duces upward and downward movement is that which 
produces weight and lightness, and that which is moved 
is that which is potentially heavy or light, and the move- 
ment of each body to its own place is motion towards 
its own form. (It is best to interpret in this sense the 310' 
common statement of the older writers that ' like moves to 
like'. For the words are not in every sense true to fact. 
If one were to remove the earth to where the moon now is, 
the various fragments of earth would each move not towards 
it but to the place in which it now is. In general, when 5 
a number of similar and undifferentiated bodies are moved 
with the same motion this result is necessarily produced, 
viz. that the place which is the natural goal of the move- 
ment of each single part is also that of the whole.^ But 
since the place of a thing is the boundary of that which 
contains it, and the continent of all things that move 
upward or downward is the extremity and the centre, and 
this boundary comes to be, in, a sense, the form of that 10 
which is contained, it is to its like that a body moves when 

^ Reading d ovu els with EL (Simplicius' MSS. had, some el ^xh ds, 
and some fl /xeV. J has eh ovv). The apodosis does not begin till 
310^^ 16 TO 8e Cn'^elv, the argument being interrupted by a long note on 
the meaning of the saying onoiov npos ofxoiov, which should be marked 
as a parenthesis. 

^ coa9' oTTov . . . TO Tvav is explanatory of tovto o-vji^aiveiv. Gram- 
matically the predicate to be supplied to t6 rrau is 7re(f)VKe (f)epeadai, 
though this in the context creates a slight illogicality. Aristotle's 
point is that a fragment of earth moves to the mass called the earth, 
not because it loves its like, but ^er accidens in the effort to reach the 
centre. It is the effort of numberless such fragments to reach 
the centre which has formed the mass, not the presence of the mass 
at the centre which causes the effort. 



3i6^ DE CARLO 

it moves to its own place. For the successive members of 
the series ^ are like one another : water, I mean, is like air 
and air like fire, and between intermediates the relation 
may be converted, though not between them and the 
extremes ; thus air is like water, but water is like earth : ^ 
15 for the relation of each outer body to that which is next 
within it is that of form to matter.^) Thus * to ask why fire 

^ €(})e^rjs should be read, with the other MSS. and Simplicius, rather 
than E's e^ijs. Cf. de Gen. et Co7t. 331^4, 26, 34. 

^ i. e. though air is Hke fire, fire is not like air ; and though water is 
like earth, earth is not like water. See next note. Prantl proposes 
to take jLieo-oty and (kpois in 1. 13 to mean inner and outer respectively, 
i. e. to make the former stand for earth and water, the latter for fire 
and air. His reason is grammatical : /ueVoi? is in the dative and so 
are vdan and yfj. Thus a construction is provided for fxeaois. He 
omits to observe that toIs S" aKpois ov becomes meaningless : which, 
with the admitted difficulty of taking the terms in this sense, is 
sufficient reason for rejecting the proposal. It is no doubt due to 
ojioia that jj-eo-ois is in the dative : likeness to a /xeVor is convertible, 
likeness to an aVpoi/ not. 

^ The connexion is difficult, and may be explained as follows. 
Aristotle's argument is formally concluded at (})epeadat in 1. 11 (*to its 
own place '). The ' place ' (centre and extremity, as explained) gives 
form to the body, and the body in reaching its place attains its form, 
i. e. completes the transition from potentiality to actuality. In a sense, 
then, if the potential is like the actual, it moves ' to its like '. The ydp 
in 1. II forestalls an objection. 'There remain the intermediate 
bodies : what of them ? ' These are given form or determined by 
the extreme bodies, and thus mediately determined by the 'place'. 
Instead of saying 'are given form ' or ' are determined' Aristotle says 
' are like '; being entitled to do so by the meaning just given to ' like '. 
The like to which earth moves is that from which it receives its form, 
and the Hke to which water and air move is the extreme body — earth 
in the one case, fire in the other— from which each receives its form. 
Thus 'like' means 'receptive of form from'. In this sense water 
is like air which is like fire, and air is like water which is like earth ; 
but the extremes themselves, earth and fire, are like nothing but their 
places. The relation of likeness is reciprocal (i.e. determination is 
mutual) only between the intermediates ; and the chain of resemblance 
breaks off in each direction short of the extreme. Starting from the 
centre, we find in the three terms, water, air, fire, a gradual approxima- 
tion (del TO uvcorepov . . .) to the form realized in fire ; starting from the 
extremity, we find in the terms air, water, earth, a gradual approxima- 
tion to the form realized in earth. (Of these two complementary 
statements Aristotle gives only the first ; but the second is necessary 
to complete the argument.) Therefore the intermediate bodies, as 
well as the extremes, may be said in moving to their places to attain 
. their form. — The above account agrees in principle with that of 
Simplicius, who, however, is not very clear. Alexander, he tells us, 
took another view, based on a different interpretation of del to 
(\u6)T€pov ktX. As reported the view is not easy to fit into the 
context. For the relation of upper to lower bodies, cf. 312^*15 and 
/Je Gen. et Co7'r. 335"' 18. 

^ Alexander's 6)7 for fie here, like his twv (iX\o)p for Tovroiv in 1. 22, 



BOOK IV. 3 310 

moves upward and earth downward is the same as to ask 
why the healable, when moved and changed qua healable, 
attains health and not whiteness ; and similar questions 
might be asked concerning any other subject of alteration. 
Of course the subject of increase, when changed qua in- 20 
creasable, attains not health but a superior size. The same 
applies in the other cases. One thing changes in quality, 
another in quantity : and so in place, a light thing goes 
upward, a heavy thing downward. The only difference is 
that in the last case, viz. that of the heavy and the light, 
the bodies are thought to have a spring of change within 25 
themselves, while the subjects of healing and increase are 
thought to be moved purely from without. Sometimes, 
however, even they change of themselves, i.e. in response 
to a slight external movement reach health or increase, as 
the case may be. And since the same thing which is heal- 
able is also receptive of disease, it depends on whether it is 3° 
moved qua healable or qua liable to disease whether the 
motion is towards health or towards disease. But the 
reason why the heavy and the light appear more than 
these things to contain within themselves the source of 
their movements is that their matter is nearest to being. 
This is indicated by the fact that locomotion belongs to 
bodies only when isolated from other bodies,^ and is generated 
last of the several kinds of movement; in order of being 
then it will be first. Now whenever air comes into being 311^ 
out of water, light out of heavy, it goes to the upper place. 
It is forthwith light : becoming is at an end, and in that 
place it has being.- Obviously, then, it is a potentiality, 

was advanced as a conjecture unsupported by I\ISS. None of our 
]MSS. have either. The apodosis to the protasis introduced by d in 
310^31 begins here. S77 is therefore attractive, but 8e in apodosi 
is easily excused in view of the long intervening parenthesis. 

^ The use of a-no\^\v\xkvaiv ('isolated') is interesting, as Prantl 
points out, because of its later technical use (= absolutus, absolute). 
Simplicius here takes it to stand for complete substances {SXoKXrjpcov 
Kar' ovaiav ovrcou) not involved in any process of yeVeo-tr, av^rja-is, or 
dWoicoats. Prantl says aTroXeXv/diua means ' independent beings ' 
(unabhangige Wesen). Bonitz, 7nd. 84* 26, says ' idem fere ac otto- 
K€Kpifj.€Pov, x«i>pto"Toz^ '. The ' Independence ' intended is rather physical 
than metaphysical. 

^ Read exet ea-TLV. 



311^ DE CAELO 

5 which, in its passage to actuality, comes into that place and 
quantity and quality which belong to its actuality.^ And 
the same fact explains why what is already actually fire 
or earth moves, when nothing obstructs it, towards its own 
place. For motion is equally immediate in the case of 
nutriment, when nothing hinders, and in the case of the 
thing healed, when nothing stays the healing. But the 
10 movement is also due to the original creative force and to 
that which removes the hindrance or off which the moving 
thing rebounded, as was explained in our opening discus- 
sions, where we tried to show how none of these things 
moves itself^ The reason of the various motions of the 
various bodies, and the meaning of the motion of a body to 
its own place, have now been explained. 

15 We have now to speak of the distinctive properties of 4 
these bodies and of the various phenomena connected with 
them. In accordance with general conviction we may dis- 
tinguish the absolutely heavy, as that which sinks to the 
bottom of all things, from the absolutely light, which is that 
which rises to the surface of all things. I use the term 
' absolutely ', in view of the generic character of ' light ' and 
' heavy ',"' in order to confine the application to bodies 
which do not combine lightness and heaviness. It is 

30 apparent, I mean, that fire, in whatever quantity, so long 
as there is no external obstacle, moves upward, and earth 
downward ; and, if the quantity is increased, the movement 
is the same, though swifter. But the heaviness and light- 
ness of bodies which combine these qualities is different 
from this, since while they rise to the surface of some bodies 
they sink to the bottom of others. Such are air and water. 
Neither of them is absolutely either light or heavy. Both 

25 arc lighter than earth — for any portion of either rises to the 
surface of it — but heavier than fire, since a portion of either, 
whatever its quantity, sinks to the bottom of fire ; compared 
together, however, the one has absolute weight, the other 

' Omitting, with F, the words k(u ottov, which I assume to have 
been inserted by some one who mistook ov = 7idi for the genitive of 
the relative. 

2 /'/lys.VU. 1,241^24] VIII. 4, 254^^7. 

' i.e. because there are distinct species of hght and heavy. 



BOOK IV. 4 3"^ 

absolute lightness, since air in any quantity rises to the sur- 
face of water, while water in any quantity sinks to the 
bottom of air. Now other bodies are severally light and 3° 
heavy, and evidently in them the attributes are due to the 
difference of their uncompounded parts: that is to say, 
according as the one or the other happens to preponderate 
the bodies will be heavy and light respectively. Therefore 
we need only speak of these parts, since they are primary 
and all else consequential : and in so doing we shall be 35 
following the advice which we gave ^ to those who attribute 
heaviness to the presence of plenum and lightness to that of S^^ 
void. It is due to the properties of the elementary bodies 
that a body which is regarded as light in one place is 
regarded as heavy in another, and vice versa. In air, for 
instance, a talent's weight of wood is heavier than a mina 
of lead, but in water the wood is the lighter. The reason 
is that all the elements except fire have weight and all but 5 
earth lightness. Earth, then, and bodies in which earth 
preponderates, must needs have weight everywhere, while 
water is heavy anywhere but in earth, and air is heavy 
when not in water or earth. In its own place each of these 
bodies has weight except fire, even air. Of this we have 
evidence in the fact that a bladder when inflated weighs lo 
more than when empty. A body, then, in which air pre- 
ponderates over earth and water, may well be lighter than 
something in water and yet heavier than it in air, since such 
a body does not rise in air but rises to the surface in water. 

The following account will make it plain that there is an 15 
absolutely light and an absolutely heavy body. And by 
absolutely light I mean one which of its own nature always 
moves upward, by absolutely heavy one which of its own 
nature always moves downward, if no obstacle is in the 
way. There are, I say, these two kinds of body,^ and it is 
not the case, as some ^ maintain, that all bodies have weight. 

■^ Above, 309^ 20 : if they would only give an account of the simple 
bodies, their questions as to the composite would answer themselves. 

^ Read eVri nva (E and Simpl. omit nva). 

' This view is maintained in its most unqualified form by those 
(atomists, probably) who distinguish the four elements by the size of 
their particles (cf. c. ii. 310*9). 

645.20 K 



311^ DE CAELO 

Different views are in fact agreed that there is a heavy 
body, which moves uniformly towards the centre. But 

20 there is also similarly a light body.^ For we see with our 
eyes, as we said before,^ that earthy things sink to the 
bottom of all things and move towards the centre. Bat 
the centre is a fixed point. If therefore there is some body 
which rises to the surface of all things — and we observe 
fire to move upward even in air itself, while the air remains 
at rest ^ — clearly this body is moving towards the extremity. 
It cannot then have any weight. If it had, there would be 

25 another body in which it sank : and if that had weight, 
there would be yet another which moved to the extremity 
and thus rose to the surface of all moving things.* In fact, 
however, we have no evidence* of such a body. Fire, then, 
has no weight. Neither has earth any lightness, since it 
sinks to the bottom of all things, and that which sinks 
moves to the centre. That there is a centre ^ towards which 

30 the motion of heavy things, and away from which that 
of light things is directed, is manifest in many ways. First, 
because no movement can continue to infinity. For what 
cannot be can no more come-to-be than be, and movement 
is a coming-to-be in one place from another. Secondly, 
like the upward movement of fire, the downward movement 

35 of earth and all heavy things makes equal angles on every 

side with the earth's surface ^ : it must therefore be directed 

312^ towards the centre. Whether it is really the centre of the 

earth and not rather that of the whole to which it moves, 

may be left to another inquiry, since these are coincident.' 

^ It cannot be right to print 11. 14-19, Xeyco S' . . . K.nv<pov, as a 
parenthesis, with Prantl. The sentences are not sufficiently self- 
contained nor closely enough inter-connected to justify such treatment. 
The argument which begins in 1. 19 with opooixev yap is a justification 
of the statement last preceding : as there is, by general admission 
and by the evidence of observation, a heavy body, so there is a light 
body. 

2 Above, 311=^20. 

" Since the air is at rest, the explanation that the fire is 'forced up' 
{iK6\i(io^iv()v, 310*10) is inadmissible. 

* Reading "> with the MSS. Prantl's conjecture, 01% is unnecessary. 

^ Read fVn for fVri. 

" i. e. the line of movement is at right angles to any tangent. 
Cf. above, 296*' 20, 297** 19. 

"' The question is discussed in II. xiv, 296'^ 9. 



BOOK IV. 4 312* 

But since that which sinks to the bottom of all things moves 
to the centre, necessarily that which rises to the surface 
moves to the extremity of the region in which the move- 5 
ment of these bodies takes place. For the centre is opposed 
as contrary to the extremity, as that which sinks is opposed 
to that which rises to the surface. This also gives a reason- 
able ground for the duality of heavy and light in the spatial 
duality centre and extremity. Xow there is also the inter- 
mediate region to which each name is given in opposition 
to the other extreme. For that which is intermediate 10 
between the two is in a sense both extremity and centre.^ 
For this reason there is another heavy and light ; namely, 
water and air. But in our view the continent pertains to 
form and the contained to matter : and this distinction is 
present in every genus.- Alike in the sphere of quality 
and in that of quantity there is that which corresponds 15 
rather to form and that which corresponds to matter. In 
the same way, among spatial distinctions, the above belongs 
to the determinate, the below to matter. The same holds, 
consequently, also of the matter itself of that which is 
heavy and light : as potentially possessing the one character, 
it is matter for the heavy, and as potentially possessing the 
other, for the light. It is the same matter, but its being is 
different, as that which is receptive of disease is the same as 20 
that which is receptive of health, though in being different 
from it, and therefore diseasedness is different from 
healthiness.^ 

5 A thing then which has the one kind of matter is light 
and always moves upward, while a thing which has the 

^ Read ean yap w?, omit io-TL after afiff^orepcov, and put a colon af:er 
p.€Ta^v. (] has an erasure in the position of the second ecrr/.) 

- i.e. in every category. For this use of yevos see Bonitz, //id. 
152^ 16. 

^ The doctrine here expressed is the same as that expressed in the 
last chapter (310^15, note). A single matter is receptive of two 
opposed forms, weight and lightness or health and disease But 
Aristotle here adds the new point that of two such alternative forms 
one is always more formal and the other more material. Weight and 
hghtness, disease and health, are not true coordinates. A form, we 
may say, is realized in disease, in weight, in the female ; but t/ie f-rm 
is realized in health, in lightness, and in the male. The principle 
is stated in the Metaphysics in the form twv eVa^n'toj/ 17 kripix (nGroiyia. 
(TTiprjcns (1004^27). 

K 2 



312^ DE CAELO 

opposite matter is heavy and always moves downward. 
Bodies composed of kinds of matter different from these 
but having relatively to each other the character which 

25 these have absolutely, possess both the upward and the 
downward motion.^ Hence air and water each have both 
lightness and weight, and water sinks to the bottom of 
all things except earth, while air rises to the surface of all 
things except fire. But since there is one body only which 
rises to the surface of all things and one only which sinks 
to the bottom of all things, there must needs be two other 

3° bodies which sink in some bodies and rise to the surface of 
others. The kinds of matter, then, must be as numerous as 
these bodies, i. e. four, but though they are four there must 
be a common matter of all — particularly if they pass into 
one another — which in each is in being different. There 
3^2^ is no reason why ^ there should not be one or more inter- 
mediates between the contraries, as in the case of colour ; 
for ' intermediate ' and ' mean ' are capable of more than 
one application.^ 

Now in its own place every body endowed with both 
weight and lightness has weight — whereas earth has weight 
5 everywhere — but they only have lightness among bodies to 
whose surface they rise. Hence when a support is with- 
drawn such a body moves downward until it reaches the 
body next below it, air to the place of water and water to 
that of earth. But if the fire above air is removed, it will 
not move upward to the place of fire, except by constraint ; 
and in that way water also may be drawn up, when the up- 

10 ward movement of air which has had a common surface with 
it is swift enough to overpower the downward impulse of 
the water. Nor does water move upward to the place of 
air, except in the manner just described. Earth is not so 
affected at all, because a common surface is not possible to 

* In 1. 24 put the comma afto., not before, aTrXcos-. (The correction 
is due to Mr. Ross.) The intermediates, air and water, are only 
relatively light and heavy. In the absolute sense these characters 
belon;; only to fire and water. 

"^ ovdi in IJtkker and Prantl must surely be a misprint for ov8(v 
(so J). 

° 'Intermediate' stands for a region, not a point, and includes as 
a rule a variety of things. 



BOOK IV. 5 312 

it.^ Hence water is drawn up into the vessel to which fire 
is applied, but not earth. As earth fails to move up- 
ward, so fire fails to move downward when air is withdrawn 15 
from beneath it : for fire has no weight even in its own 
place, as earth has no lightness. The other two move 
downward when the body beneath is withdrawn because, 
while the absolutely heavy is that which sinks to the 
bottom of all things,^ the relatively heavy sinks to its own 
place or to the surface of the body in which it rises, since it 
is similar in matter to it.^ 

It is plain that one must suppose as many distinct species 20 
of matter as there are bodies. For \i, first, there is a single 
matter of all things, as, for instance, the void or the plenum 
or extension or the triangles, either all things will move up- 
ward or all things will move downward, and the second 
motion will be abolished. And so, either there will be no 
absolutely light body, if superiority of weight is due to 
superior size or number of the constituent bodies or to the 25 
fullness of the body : but the contrary is a matter of obser- 
vation, and it has been shown that the downward and 
upward movements are equally constant and universal : or, 
if the matter in question is the void or something similar, 
which moves uniformly upward, there will be nothing to 
move uniformly downward. "^ Further, it will follow that 

^ The surface of earth is too rough to allow of the necessar)^ avfjiCpvcrLs; 
(Simpl.), or continuity of surface, with another body. 

^ Read ianv o (not eanu, o with Bekker). Prantl's ingenious 
conjecture, ds rrjv vtto, is not quite convincing. 

^ The downward movement of earth (absolute weight) is quite 
determinate, having its limit at the centre. But the downward move- 
ment of air and water (relative weight) is not equally determinate : 
it is limited only by the surface of the body next beneath, air by that 
of water, water by that of earth, the upper body being attracted to the 
lower by similarity of matter. This admission inflicts some damage 
on the doctrine of ' places '—for where a body has weight it cannot be 
said to 'rest naturally' or to 'be in its place' — and also on the 
symmetry of the elements— for if the fire above air were removed 
the air would not move upward, but if the earth below water were 
removed the water would move downward. — In 1. 18 els must be 
construed with (peperai, and in 1. 19 ^ oh, more fully expressed, would 
be rj els Ti]v eKelvoav ols. The construction is difficult, and the passage 
may be corrupt. 

* The stopping of this sentence requires alteration, eap 8e in 1. 27 
is an irregular second limb to the disjunction introduced by v Koicfyov 
in 1. 23. Put a colon at nXiipr] (1. 25) and at aico (1. 2j), and delete the 
comma after TrXeiovoov (1. 25). 



312^ DE CAELO 

the intermediate bodies move downward in some cases 
quicker than earth : for air in sufficiently large quantity 
30 will contain a larger number of triangles or solids or 
particles. It is, however, manifest that no portion of air 
whatever moves downward.^ And the same reasoning 
applies to lightness, if that is supposed to depend on 
superiority of quantity of matter.^ But if, secondly, the 
kinds of matter are two, it will be difficult to make the 
intermediate bodies behave as air and water behave. 
313^ Suppose, for example, that the two asserted are void and 
plenum. Fire, then, as moving upward, will be void, earth, 
as moving downward, plenum ; and in air, it will be said, 
fire preponderates, in water, earth.^ There will then be 
a quantity of water containing more fire than a little air, 
and a large amount of air will contain more earth than 
5 a little water : consequently we shall have to say that air 
in a certain quantity moves downward more quickly than 
a little water. But such a thing has never been observed 
anywhere. Necessarily, then, as fire goes up because it has 
something, e. g. void, which other things do not have, and 
earth goes downward because it has plenum, so air goes to 
10 its own place above water because it has something else, 
and water goes downward because of some special kind 
of body. But if the two bodies^ are one matter, or two 
matters both present in each,^ there will be a certain quantity 
of each at which water will excel a little air in the upward 
movement and air excel water in the downward move- 
ment, as we have already often said. 

The shape of bodies will not account for their moving 5 
15 upward or downward in general, though it will account 
for their moving faster or slower. The reasons for this 

^ sc. in earth. 

"^ On the somewhat absurd theory that the universal 'matter' is 
void or absolute lightness. 

^ 3i2''33 — 313="- 3, oLuv . . . yi-js, is a parenthesis and should be so 
printed, with a colon, instead of a full-stop, at nXqpes and at kutu). 
This is proved by the infinitive ('x^^v (after (pairj) in 1. 3, as well as by 
the ydf) which follows. 

* viz. air and water. 

^ Prantl's Uurtpw is a misprint for Uarepco. 



BOOK IV. 6 313* 

are not difficult to see. For the problem thus raised is 
why a flat piece of iron or lead floats upon water, 
while smaller and less heavy things, so long as they are 
round or long — a needle, for instance — sink down ; and 
sometimes a thing floats because it is small, as with gold 20 
dust and the various earthy and dusty materials which 
throng the air. With regard to these questions, it is 
wrong to accept the explanation ofl"ered by Democritus. 
He says that the warm bodies moving up^ out of the 
water hold up heavy bodies which are broad, while the 313^ 
narrow ones fall through, because the bodies which offer 
this resistance are not numerous. But this would be 
even more likely to happen in air — an objection which 
he himself raises. His reply to the objection is feeble. In 
the air, he says, the ' drive ' (meaning by drive the move- 5 
ment of the upward moving bodies) is not uniform in 
direction. But since some continua are easily divided and 
others less easily, and things which produce division differ 
similarly in the ease with which they produce it, the ex- 
planation must be found in this fact. It is the easily 
bounded,^ in proportion as it is easily bounded, which is 
easily divided ; and air is more so than water, water than 10 
earth. Further, the smaller the quantity in each kind, 
the more easily it is divided and disrupted. Thus the 
reason why broad things keep their place is because they 
cover so wide a surface and the greater quantity is less 
easily disrupted. Bodies of the opposite shape sink down 
because they occupy so little of the surface, which is there- 15 
fore easily parted. And these considerations apply with 
far greater force to air, since it is so much more easily 
divided than water. But since there are two factors, the 
force responsible for the downward motion of the heavy 
body and the disruption-resisting force of the continuous 
surface, there must be some ratio between the two. For 
in proportion as the force applied by the heavy thing 

^ ava<f)€p6fx€va is the better-attested reading (ELMJ Simpl.) and 
should be preferred to avo (pepo^xeva. The word is elsewhere used 
of upward movement by Aristotle. 

^ i. e. the fluid or moist. Cp. de Geri. et Corr. 329^ 30. 



313^ DE CAELO 

20 towards disruption and division exceeds that which resides 
in the continuum, the quicker will it force its way down ; 
only if the force of the heavy thing is the weaker, will it 
ride upon the surface. 

We have now finished our examination of the heavy and 
the light and of the phenomena connected with them. 



INDEX I. Endish 

o 

[The sign + following a reference means that many other references 
could be given.] 

68-n = 268-siS- 



Above-below f up-down) — (i) in 
ref. to motion of elements = ex- 
tremity and centre 6S^ 22, 08^ 
18 + ; (2) applied to universe 
by analogy^ from animals : upper 
and lower hemispheres 85^ i ; 
above prior to below 84^ 25, 
'more divine' 88^ 5. 

Action— attributed to stars 92^ 14 ; 
most varied in man 92^ 2. 

Air — one of the two elements 
which move upward 69^ 18 + j 
one of the two intermediates 
ig-v.) ; ignited by miovement of 
stars 89^ 20 ; thought to sup- 
port the earth 94^ 14 ; assists 
movement of bodies 01^ 23. 
See also Intermediate. 

Aither — special name for the 
highest place, meaning ' what 
runs always ' 70^ 2i ; Anaxa- 
goras interprets otherwise 70^ 
24, 02*^ 4. 

All— connexion of, with number 
three 68^ 11. 

Alteration— def. m.ovement in re- 
spect of quality 70^ 27, lO'"^ 23 ; 
not applicable to fifth element 
70^ 13 : nor to any infinite 75^ 
I ; comparison with local move- 
ment, 'j']^ 14, 10^ 16. 

Anaxagoras — makes aither = fire 
70^ 24, 02^ 4 ; explains immo- 
bility of earth by flatness 94^ 
14 ; his cosmogony 01^ 11 ; his 
homoeomeries = elements 02^ 
29 ; denies existence of void 09^ 
19 ; referred to by implication 
69^ II, 74b 19, 89^ 17, 97M3. 
Anaximander — explains immobi- 
lity of earth by indifference 95^ 
10; referred to by implication 
98^ 33 ; reference doubted 03^ 

13. 
Anaximenes — explains immobility 
of earth by flatness 94^ 14; re- 



ferred to by implication 98^ 33, 
03^ 12. 

Animals — growth of, 70^ 31 ; spa- 
tial oppositions in, 84^ 11 ; phy- 
sical composition 88^ 1 5 ; organs 
for movement 90^ 30 : compari- 
son with stars 90^ 30, 92^ i, 
93^6. 

Astronomy — A.'s conception of, 
gi^ 30^ 21, 97'^ 4 : astronomical 
records of Eg>'pt and Babylon 
70^ 14, 92^ 7. 

Atlas — not required 84^ 20. 

Atoms — (of Democritus and Leu- 
cippus) differ only in shape 75^ 
30, 03^ 10 ; in perpetual move- 
ment 00^ 9 ; infinite in number 
03^ 5 ; in conflict with fact 04^ 
25, with mathematics 03'^ 25. 
See also Democritus, Leucippus. 

Babylonians — their astronomical 

records 92'^ 7, jo"^ 14. 
Below — sje Above. 

Category — 81^ 32, 12^^ 14. 

Centre — of earth )( of universe 96^ 
10, 12^ I ; goal of movement 
of heavy bodies 68^ 21, 69^ 23, 
76^ I, 97^ 5, 11^ 29; Pythago- 
rean view of 93'"^ 20. See also 
Earth. 

Chance— 83^^ 32, 87^ 25,_89t> 23. 

Circles (or spheres) — solid revolv- 
ing bodies, composed of the 
primary body, in which the stars 
are fixed 89^ i, 92^ 26; also 
called ' heavens ' and ' motions ' 
[q.Z'.). 

Coan (? Chian) throw — 92^ 30. 

Coincidenceof predicates— 82'^ 30. 

Commensurability — of weights 
73^ 10 : of bodies 04^ 25 : of 
diagonal Si'* 5, ^7. 

Complete— defined 86^ 20 (cf. 71^ 
31.68^1. 



INDEX 



Continuum— 68^ 7, 80^ 20, 06^ 
24, 13^ 6. 

Contrary— c.s exist together and 
have same matter 86* 22 ; c.s 
essential to generation 70* 13 • 

- c.s admit of intermediates 12^ 
I ; examples, unnatural) (natu- 
ral movement 69* 9 + , upward )( 
downward movement 73* 7 +, 
hot )( cold 07^ 6, spatial 71* 26, 
87^ 6 ; c. relations between any 
two elements 86* 30 ; no c. to 
circular movement 70^ 31, to 
any figure 07^ 7. 

Counter-earth — supposed by Py- 
thagoreans 93* 25. 

Cyprus — 98* 4. 

Decay — see Generation. 

Democritus— supposes the uni- 
verse not continuous 75^ 30; 
explains immobility of earth by 
flatness 94^ 14 ; views in regard 
to movement 00^ 8, to elements 
03* 4, to generation 05* 35 ; 
makes the sphere a kind of 
angle 07* 17 ; his explanation 
of floating 13* 21 ; associated 
with Leucippus 75^ 30, 00^ 8, 
03* 4; referred to by implica- 
tion ']f^ I (extrusion), 79^ 13 
(destructible world), 08^ 30 
(void). See also Atoms, Drive, 
Extrusion, Void. 

Dense-rare— 99^ 8, 03* 12, ^ 23. 

Differences— importance of study- 
ing 94^ 12 ; number limited 
03a I. 

Diminution— j^^ Increase. 

Divination — = inspired guess 84^ 
5 ; uses opposition right )( left 
85*2. 

Divisibility — conditions of 68* 25, 
13^ 6; consequences of denial 
of 99* 17. 

Drive — term used by Democritus 

Duration — special name for the 
life of the universe, implying 
eternal existence 79* 23. 

Earth — (i) the element : moves 
naturally to the centre and rests 
there 69* 27, 86* 20, 95^ 20 + ; 
absolutely, not merely rela- 
tively, heavy li* 15; ace. to 
the theory of planes the only 



true element 06* 18.-^(2) the 
central mass : its central posi- 
tion 93* 17 ; its immobility 93^ 
16, 94* 12, 96* 24; its spheri- 
cal shape 93^ 33, 97* 9, con- 
firmed by shadow on the moon 
97^ 25 ; its size 97^ 31 ; view of 
Pythagoreans (in motion about 
the centre) 93* 20 ; of Plato, 
TUnaeiis (similar) 93^ 31, 96* 
24 ; of Xenophanes (infinite 
deeps) 94* 22 ; of Thales (floats 
on water) 94* 28 ; of Anaxime- 
nes, Anaxagoras, Democritus 
(immobile because of its flat- 
ness) 94^ 14 ; of Empedocles 
(immobile because of the vor- 
tex) 95* 15 ; of Anaximander 
(immobile because of its indif- 
ference) 95^ 10. 
Eclipse — of moon more frequent 
than of sun (Pythagoreans) 94^ 
23 ; of moon by earth gives 
curved outline 97^ 25 ; of Mars 
(or Mercury ?) by moon 92* 4. 
Egypt — astronomical records of 
92* 7, 70^ 14 ; stars seen in 
98* 4. 
Elements — normally called ^ sim- 
ple bodies ' 98* 30, 02^ 7, 06^ 
4 + ; specifically distinct parts 
6'^' 5, 14; possess a principle 
of movement 68^ 28 ; three in 
number, 'j']'^ 14, 98^ 8 ; their 
distinction depends on natural 
movements 76^ 8, 04^ 20, and 
places ']']^ 14 (cf. 12^' 19). — 
(i) the primary body, substance 
of the outer heavens (Bks. I, 
II) : moves naturally in a circle 
69* 5, a sign of its perfection 
69* 16 ; neither light nor heavy 
69* 19; not subject to genera- 
tion, increase, or alteration 70* 
12, 88* 34 ; not infinite 71^ i ff. ; 
its several movements 86* 3, 
89*^ I, 91^ 30; why spherical 
86^ 10; direction of movement 
Z^j^ 22 ; regularity of movement 
88* 14; substance of the stars 
89* 13 ; its movement the mea- 
sure of all movement 84* 2, 87* 
23. — (2) below the moon (Bks. 
Ill, IV): primary constituents 
of bodies 02* 11 ; four in num- 
ber (earth and fire, with two 
intermediates, water and air), 



INDEX 



but treated as two, yy^ 14, qS'^ 
8 ; based on opposition light )( 
heavy 01^ 22, 07^ 28 ; their 
natural movement 00^ 20, 10^ 

14 ; a passage to form, being, 
or actuality 10^ i, 11^ 4; their 
serial character 10^ 11 ; dis- 
tinctive properties 11^ 15 ; in- 
volve generation 70^33, 98^ 10, 
02* 10, 04^ 23 ; pass into one 
another 05* 14; not infinite in 
number 02^ 10 ; nor reducible 
to one 03^ 14 ; not distinguish- 
able by size 04* i ; nor by shape 
06^ 3. — Views of others : early 
thinkers 03^ 13 ; Anaxagoras 
02^ 29; Empedocles 95* 31, 
02^ 30, 05^ I ; Leucippus and 
Democritus 03* 3 ; Plato, Tt- 
maeus 06^ I. 

Elephants— found in India and in 

N. Africa 98^ 12. 
Empedocles — his views on the 

destructibility of the world 79^ 

15 ; on the immobility of the 
earth 84^ 24, 94^ 25, 95a 8, 30, 
00^ 2 ; on the elements 02^ 29, 
^23,05*35 ; ignores opposition 
light )( heavy 09^ 19 ; his prin- 
ciples ' Love ' and ' Hate ' 80*^ 
16, 95^ 31, 00^ 29, oi* 16; 
quoted 94^ 25 , 00^ 30. See also 
Vortex, Excretion- 
Excretion— process by which Em- 
pedocles accounts for the gene- 
ration of the elements 05^ i. 

Extrusion — forced motion of a 
body due to action of other 
bodies, a term used by ' some 
writers ' (Leucippus and Demo- 
critus?) jy^ I. 

Form— opp. matter yZ^ i, 10^ 15, 
12* 12 ; Platonic 78* 16. 

Front-back— applied to universe 
84b 21, 88*6. 

Generation— depends on inter- 
action of contraries 70* 15; 
hence excluded from sphere of 
the primary body 70* 19, 79^ 4, 
88* 34 ; necessity of, below the 
moon 70* 33, 98^ 10, 02* 10 ; 
g. of elements from one another 
04^ 24, 05* 34 ; not absolute 
01^ 2 ; not admitted by Melis- 
sus and Parmenides 98^ 1 5. 



Geometry — construction in 79^ 35. 

God — as creative 71* 33 ; his ac- 
tivity eternal life 86* 9 ; popu- 
larly connected with the hea- 
vens 70^ 7, 84* 12 ; use of 
number 3 in worship of 68* 15. 

' Harmony of the spheres ' — a Py- 
thagorean view, refuted 90^ 12. 

Hate — (in Empedocles) >y<?^ Love. 

Heaven — three senses distin- 
guished 78^ 10 ; sense [a] ' first ' 
or 'outermost' h. 70^ 15, 88* 
15, 92^ 22, 98* 24 (cp. 91* 35, 
91^2); 'fixed' h. 72^31; — sense 
{b) (including the planets) ani- 
mate 85* 29, Divine 86* 10, 
spherical ^10, eternal, ^y^ 26 ; 
— sense {c) (=world, universe) 
90* 6, 98* 31, 00* 15, 01* 17, 
03^ 13, 08* 17; hemispheres 
85^ 10, 08* 26 ; includes all 
body, place, time, 76* 18, y2>^ 
26,79-^12. See aIso'E\e,jxitnis{i). 

Heavy-light— applied to bodies 
which move naturally towards 
and away from the centre 69^ 
20 ; imply a finite system y^,^ 
22 ; not applicable to primary 
body 69^ 19, 76* 16; not ac- 
counted for by Empedocles 95* 
30 ; nor by the theory of planes 
99* 24 ; dist. absolute-relative 
08* 7 ; heavy the privative, 
light the positive term 86* 26. 

Heraclitus— on generation 79^ 15, 
98^ 30 ; referred to by implica- 
tion 03^ 12 (cf. 04* 18). 

Hercules, Pillars of — 98* 11. 

Hesiod — on generation 98^28 (cf. 
79^ 13). 

Hippasus— 03^ 12. 

Hippon— 03^ II. 

Homoeomeries — of Anaxagoras 
02* 31, 04* 26. 

Hydrarpax — name for water- 
clock in Simpl.'s day 94^ 21. 

Hypothesis— dist. false-impossi- 
ble 8ib 4. 

Idaios — of Himera 03^ 13. 
Increase-diminution — 70* 23, 84^ 

28, 88^ 15, 10*27, 10^ 20. 
India— 98* 11. 

Indivisible lines — 99* 10, 07* 22. 
Infinite — not predicable of body 

71^ 2 IT. ; of weight y^^ 22 ; of 



INDEX 



elements 03^ 5 ; of process of 
analysis 04^ 28 ; not to be tra- 
versed 00^ 4 ; as applied to line 
69^ 22, 72^ 17; i. shapes, ace. 
to Democritus 03^ 12. 
' Intermediate — bodies (viz. air and 
water) 76^ i, 86* 29, 10^ 12, 
12^28; places (i.e. where these 
bodies rest) TJ^ 23, 12* 9; i. 
body cannot be primary 03^ 22 ; 
between contraries 12^ i. 
Ixion — 84* 35. 

Klepsydra— 94^ 22. 

Leucippus— conjoined with Demo- 
critus 75^ 30, 00^ 8, 03* 4 (cf. 
77^1, 08^ 30). See also Demo- 
critus. 

Light— J^^ Heavy. 

'Like to like' — means matter to 
form 10^ I. 

Love-hate— opposed causal prin- 
ciples in cosmology of Empedo- 
cles 80* 16, 95* 31, 00^ 29, oi'^ 
16. 

Magnitude— complete in three 
dimensions 68* 9 ; simple, two 
only, viz. straight and circular 
line 68^ 19; minimum, impos- 
sible 71^ 10. 

Mars — (or Mercury.^) eclipse of, 
by moon, observed by A. 92* 5. 

Mathematics — contributions of, to 
astronomy 91^ 9, 97* 4, 98* 16 ; 
admits no minimum 71^ 10; 
its principles finite 02^ 30 ; in 
conflict with the atomic theory 
03* 21 ; with the theory of 
planes 06* 28 ; the mathemati- 
cal the most accurate sciences 
06* 28. 

Melissus — and Parmenides de- 
nied generation 98^ 17. 

Minimum— no m. magnitude 71^ 
10 ; no m. time 74* 9 ; m. move- 
ment the measure Z']'-^ 23 (cf. 

881^31)- 

Missiles— movement of 88^*^ 23, 
89* 23. 

Moon -phases 91^' 20; move- 
ments 91^ 35; so-called face 
90* 26.. 

Motion— = circle {q.v) to which 
stars are attached 79* 20, 92=^ 
14. 



i Movement — physics concerned 
j with 68* 2, 08* I ; not present 
I in all things 98^ 19 ; of three 
j kinds, qualitative, quantitative, 
j local 10* 23. 

— (i) local : belongs naturally to 
all bodies 68^ 15 ; finite in 
character 77* 17 ; dist. natural- 
I constrained 76* 22, 94^ 32, 00* 
20 + ; dist. simple-compound 
68^ 30, 00* 20 + ; kinds of 
simple m. 68^ 17 ; (i) circular 
70^ 31, ir 3, 84^ 4'86i>2 + ; 
(ii) rectilinear 10* 14 + ; down- 
ward, goal of 96^ 7 ; ' makes 
equal angles ' 96*^ 20, (^f^ 19. 
— of heavens : variety 86* 3, 91^ 
29; direction Z']^ 22; regu- 
larity 88* 14; w. ref. to stars 
89b I. 
—of animate things 84^ 32, 85* 
29 ; of spherical bodies 90* 9, 
91^15; as cause of fire 89*21. 
— (2) qualitative— J^^ Alteration; 

' sense-m.' 84^ 29. 
— (3) quantitative — see Increase. 
— ' discussion of m.'^Phys. V- 
VIII 73* 20, 75^ 23, 99* 10; 
j ' of time and m. ' 03* 23. 

I Nature — as agent 68* 20, 71* 33, 

88*3, 90* 30, 91* 25, ^14, 93a 

{ 2 ; as form 86* 18, 01* 8 ; as 

I source of movement 68'' 16, 01^ 

i 17 + ; perfection of 88* 9 ; order 

of 03^^ 19; inquiry into 68* i, 

i 98b I. 

Numbers — allotted to geometrical 

figures 86^' 34 ; compose the 

world, ace. to Pythagoreans 00* 

15 ; the n. three 68* 15. 

Ocean — unity of 98* 10. 
Orpheus — cosmogony of 79*^ 13, 

98^ 27. 

Parmenides — and Melissus de- 
nied generation 98^ 17. 

Philosophy — first J']^^ 10 ; popular 
79^31. 

Physics of Aristotle — cited as 
'opening discussions' 70* 17, 
11*12; Bks. I-IV cited as * dis- 
cussion of principles ' 72* 30 n., 
74* 21; Bks. N-YUl as 'dis- 
cussion of movement ' 72* 30, 
75'' 23, 99* 10; as * d. of time 



IXDEX 



and m/ 03^ 23 ; treated gener- 
ally as continuous \v. De Caelo 
73a 18, 85a 28, 86^ 20, 05a 22 + . 

Place — belongs to the perceptible 
75^ II ; contrarieties of 71^ 5, 
26, 73^ 12; proper or natural 
76^ 12, 10^ 7 ; intermediate j']^ 
23, 11^ <^', w. ref. to void 09^ 
26 ; none outside the heaven 
79* 12. 

Planes, theor>' of— 86^ 27. 98^ ^}„ 
06*1. 

Planets — secondary revolution of 
85^ 29, 91^ I ; absence of twink- 
ling 90* 19. See also Heaven. 
Mars. 

Plato— (not mentioned by name) 
his Timaetis cited 80* 30. 93^ 
32, GO* I, ^ 17, c6^ 19, c8^ 4. 

Poles— 85^ 10, 93b 32, 96^ 27. 

Possibility — notion of, examined 
81*1, 83^ 8 : no unrealized p. 

Principle — in logical sense 71^ 12. 
02^ 27. 03* 18. 06* 7 ; structur- 
al, in animals 84^ 11, 85^ 20; 
in geometrical figures 03^2 ; of 
movement 68^ i6_, 84^ 32, 85^ 
29, ^7; "discussion of p.s' = 
Phys. I-IV 74^ 21 (cf. 72* 30 n. •. 

Privation — 86^ 26. 

P}Tamid — 03^ 32. 04^ 12, ^4, 06^ 

Pythagoreans — on the number 
three 68'^ 11 ; on right and left 
in the heaven 84^ 7 ; on the 
hemispheres 85^ 26; on the 
motion of the earth 93* 20 ; 
their 'counter-earth' 93* 25, 
^ 20 ; ' Guard-house of Zeus ' 
93^ 4 ; compose the world of 
numbers co* 15 ; cf. also 90^^ 15 
(' harmony of the spheres ' i. 

Right-left— applied to universe 
84^ 6 ; motion of first heaven 
starts from right and moves to 
ri^ht ^-^ 17 : right prior to left 
88=^ 6. 

Rohing — a motion appropriate to 
a sphere 90^ 10 

Sense-movement — 84^ 29. 

Sound — said to be unheard if con- 
tinuous 90^ 27 ; has physical 
effects 90 "0 34. 

Spheres — the primary shape 86^ 



10 : suitea omy to movement 
in one place 90^ 2 ; its proper 
movements 90* 10 ; spherical 
shape of universe 87^ 15, 90^ i ; 
of stars 90^ 8, ^i, 91^ 10; of 
the earth 97*^ 21 ; of surface of 
v/ater 87^ i : (supposed) of par- 
ticles of fire 06^^ 33 ; ' harmony 
of the s.s ' 90" 12. See also 
Circles. 

Spinning — a motion appropriate 
to a sphere 90^ 10. 

Stars — composition, 89* 15 ; car- 
ried on moving spheres 89^ 29, 
^ 31 ; distances 91^ 30 ; speed 
of motion 91^ 33 : shape 91° 10; 
distribution 92^ 10 ; number of 
movements 91^ 30 ; unchang- 
ing intervals ^Z"^ 10, 96^ 4; 
twinkling (dist. planets 1 90* 18 ; 
seen differently in different 
countries 97^ 31 ; comparison 
with animals 90* -^o. 92^ i? 93^ 6. 

Substrate— 70^ 16, c6^ 17. 

Sun— its heat 89^ 32 ; apparent 
spinning motion 90^ 15 ; echpses 
of, by moon 91^ 23 ; number of 
movements 92=^ i ; distance 

94" 4- 
Suspension — of triangles 06^^ 22. 

Text — (basis Prantl, 1881) (i) con- 
jectures adopted or suggested 
72b 17, 80b 18, 81^ I, 7, 83^ 29, 
92^ II, 95a 22, 99^ 19, 01^ 19, 
04* 28, 12* 10. 

— (2) alterations of punctuation 

68*24,73^25,74^5^11, 76^17, 
']']^ 16, 18, -jZ^ 15, 79^ 22, 26, 
80*30, ^28, 81^ 29, 82* 12, 26, 
83^ 14- 24, 29,^9,21,89-^2,23, 
92^3,. 13, 93^ 18, 95=^ 10, ^33, 
01* 19, ^ 23, 05* 28, 06^ 17, 08b 
6, 15, 10^ I, 11^ I-, 12^ 24 ^25, 

— (3) misprints corrected 76^ 5, 
18, 77^ 32, ^^27, 7S^ 16, 79^ 6, 
80* 29, 81* 16, 83b 21, 84^ 20, 
86^ 28, 91* 22, 29, 95^ 15, 06^ 
32, 07* 8, 21, 10* 20, 12* 33, 
13* II. 

— (4) other alterations 68* 22, 
^ 25, 69* 7, 23, 28, b 21, 26. 70* 
23,71*29,^5, i9oO,33.. 72^ I, 
T^i'' 16, 74^ 22, ^5, 32, 75* 10, 
76^21,77^27,78^3,28,80^34, 
8ib 18, 21, 33, 83* 17, ^5, 7, 



INDEX 



84^7,30,86^1, 19,87^27,^34, 
88^ 10, 26, 89b 28, 92^ 4, 93^ 

28, 94^ 20, 95b 4, 99b 22, 28, 32, 
01^ 9, ^ 15, 20, 02*^ 2, 12, 03^ 2, I 
04a 16,^ 27, 06^ IS, 28, 08=^ I, 
24, 32, 09^> 20, 25, 10^ 7, 31, 
^12, 16, II* 3, 6, ^16, 26, 29, 
12'' 17, 13^ 23. 

— (5) other comments 68^ 19, 70* 
26, 71* 24, 72^ 14, ^ 18, 28, 76^ 
30, 77* 2,29,31,78^ 20, 80^ 20, 

29, 83* 26, 85* 7, 88* 6, 92* 26, 
29, 93* 24. ^ 31, 96* 26, 97* 34, 
99* 19, 01^ 17, 31, 05* 17, 07* 
17, 08* 31, 10* 3, ^22. 

Thales — said earth rests upon 

water 94* 28 ; referred to by 

implication 03^ li. 
Three — mystical significance of 

the number 68* 15. 
Thunder — splits rocks by its noise 

_9o^> 35. 
Time — inconceivable outside the 

heaven 79* 14 ; no minimum t. 

74* 9 ; every performance has 

its minimum t. 88'' 32. 
Transverse — in the universe, def. 

85^ 12. 
Triangle— constituent of bodies, 

in the Tinmen s 08^ 15, 09^ 34 ; 

its Pythagorean number 87* i. 



Vegetables — liable to increase 70* 
33 ; compared with lower stars 
92^ 2. 

Visual ray— 90* 17. 

Void — supposed by Leucippus and 
Democritus to account for 
movement 00^ 10; cannot be 
the matterof things, either alone 
12*^ 21, or with plenum 13* i ; 
extra-corporeal, impossible 02* 
I, 05* 17; intra-corporeal, as 
cause of lightness 09* 6, 11^ i ; 
as explaining expansion, 05^ 17 ; 
no V. outside the heaven 79* 12 
(cf. Z^^ 15) ; has no natural 
movement 09^ 18 (cf. 13* i). \ 

Vortex (or Whirl) — supposed by 
Empedocles 84* 24, 95* 8, 00^ 3. 

Water — moves downward 69* 18 ; 
proof that its surface is spheri- 
cal 87^ I ; supposed by Thales 
to support the earth 94* 28 ; to 
be the one element 03^ 11. See 
also Intermediate. 

Water-clock -94^ 22. 



Xenocrates- possibly referred to 

79^ 33, 98^ 33- 
Xenophanes — cited 94* 22. 



INDEX II. Greek 



[The reference is to the foot-note in which the word is cited. 



avrnKoKovfia 82* 30. 
aTToAeXf/iAfVov 10^ 33. 
dtaaTrjUd 71^ 3I. 
8L0pi(eLv Ol'^ 17. 
bvvniiLi 81* 7. 
eyKVKXios 86* 12. 
€K(TT(i(ris 86* 20. 
e|corf/jiKOi Aoyot 79''^ 3'^* 



'IWeaOdL 93^^ 31. 
Kouia-is 92* 26. 
Koafios 72* 20. 
ofiOLOTrjs 95'* 1 1. 
o\lris 90* I 7. 
nXiryij 89* 28. 
crvyxoipft.i' 97^ 12. 
(poj)d 92* 14. 



DE GENERATIONE 



ET 



CORRUPT lONE 



It 

DE GENERATIONE 

ET 

CORRUPTIONE 



BY 



HAROLD H. JOACHIM 

FELLOW OF NEW COLLEGE, HONORARV FELLOW OF MERTON COLLEGE, AND 
WYKEHAM PROFESSOR OF LOGIC IN THE UNIVERSITY OF OXFORD 



OXFORD 

AT THE CLARENDON PRESS 

1922 



Oxford University Press 

London Edinburgh Glasgow Copenhagen 

Neiv Torh Toronto Melbourne Cape Town 

Bombay Calcutta Madras Shanghai 

Humphrey Milford Publisher to the University 



PREFACE 

This translation has been made from a revised text, 
which is now being published for me by the Delegates of 
the Clarendon Press as part of an edition of Aristotle's 
irepl y€V€(T€cos Kal (pOopas. I have indicated in a few brief 
footnotes the chief passages in which the readings I have 
adopted differ from those of Bekker ; a full explanation, 
and a defence of my interpretation in detail, will be found 
in my edition. 

To Mr. W. D. Ross, Fellow of Oriel College, I am 
greatly indebted for many most valuable criticisms and 
suggestions. The references in the footnotes to Burnet are 
to the third edition of that author's Early Greek Philosophy 
(London, 1920) ; and the references to Diels are to the 
second edition oi Die Fragmente der Vorsokratiker (Berlin, 
J 906). 

H.H.J. 



ANALYSIS 

BOOK I. 

cc. 1-5. Coming-to-be and passing-away are distinguished froin 
' alteration ' and from growth and diminution. 
CH. 

1. Are coming-to-be and passing-away distinct from 'alteration'? 

It is clear that, amongst the ancient philosophers, the monists 
are logically bound to identify, and the pluralists to distinguish, 
these changes. Hence both Anaxagoras and Empedokles (who 
are pluralists) are inconsistent in their statements on this subject. 
Empedokles, it must be added, is inconsistent and obscure in 
many other respects as well. 

2. There are no indivisible magnitudes. Nevertheless, coming-to-be 

and passing-away may well occur and be distinct from ' altera- 
tion '. For coming-to-be is not effected by the ' association ' of 
discrete constituents, nor passing-away by their ' dissociation ' ; 
and ' change in what is continuous ' is not always ' alteration '. 

3. Coming-to-be and passing-away (in the strict or 'unqualified' 

sense of the terms) are in fact always occurring in Nature. Their 
ceaseless occurrence is made possible by the character of 
Matter {materia prima). 

4. ' Alteration ' is change of quality. It is thus essentially distinct 

from coming-to-be and passing-away, which are changes of 
substance. 

5. Definition and explanation of growth and diminution. 

cc. 6-10. What comes-to-be is formed out of certain material con- 
stituents^ by their ^ combination \ Combination implies 'action 
and passion \ which in turn imply ' contact '. 

6. Definition and explanation of 'contact'. 

7. Agent and patient are neither absolutely identical with, nor sheerly 

other than, one another. They must be contrasted species of 
the same genus, opposed formations of the same matter. 

8. Bodies do not consist of indivisible solids with void interspaces, 

as the Atomists maintain : nor are there ' pores ' or empty 
channels running through them, as Empedokles supposes. 
Neither of these theories could account for ' action-passion '. 

9. The true explanation of ' action-passion ' depends {a) upon the 

distinction between a body's actual and potential possession of 
a quality, and [b] upon the fact that potential possession (i.e. 
'susceptibility') may vary in intensity or degree in different 
parts of the body, 
10. What ' combination ' is, and how it can take place. 



vi ANALYSIS 



BOOK 11. 

cc. 1-8. The material constituents of all that cofnes-to-be and 
passes-away a7'e the so-called ' elements ', i. e. the ' simple ' bodies. 
What these are, how they are t?'ansformed into one another, and 
how they ^combine '. 

CH. 

1. Earth, Air, Fire, and Water are not really ' elements ' of body, but 

' simple ' bodies. The ' elements ' of body are ' primary matter ' 
and certain ' contrarieties '. 

2. The ' contrarieties ' in question are ' the hot and the cold ' and 

' the dry and the moist '. 

3. These four ' elementary qualities ' (hot, cold, dry, moist) are 

diversely coupled so as to constitute four ' simple ' bodies 
analogous to, but purer than. Earth, Air, Fire, and Water. 

4. The four ' simple ' bodies undergo reciprocal transformation in 

various manners. 

5. Restatement and confirmation of the preceding doctrine. 

6. Empedokles maintains that his four ' elements ' cannot be trans- 

formed into one another. How then can they be ' equal ' 
(i.e. comparable) "as he asserts? His whole theory, indeed, is 
thoroughly unsatisfactory. In particular, he entirely fails to 
explain how compounds (e. g. bone or flesh) come-to-be out of 
his ' elements '. 

7. How the ' simple ' bodies combine to form compounds. 

8. Every compound body requires all four ' simple ' bodies as its 

constituents. 



cc. 9-10. The causes of cofning- to-be and passing-away. 

9. Material, formal, and final causes of coming-to-be and passing- 
away. The failure of earlier theories — e. g. of the ' materialist ' 
theory and of the theory advanced by Sokrates in the Phaedo — 
must be ascribed to inadequate recognition of the efficient cause. 

10. The sun's annual movement in the ecliptic or zodiac circle is the 

efficient cause of coming-to-be and passing-away. It explains 
the occurrence of these changes and their ceaseless alternation. 

Appendix. 

11. In what sense, and under what conditions, the things which 

come-to-be are 'necessary'. Absolute necessity characterizes 
every sequence of transformations which is cyclical. 



ON COMING-TO-BE AND PASSING-AWAY 

BOOK I 

I Our next task is to study coming-to-be and passing- 314^ 
away. We are to distinguish the causes, and to state the 
definitions, of these processes considered in general — as 
changes predicable uniformly of all the things that come-to- 
be and pass-away by nature. Further, we are to study 
growth and 'alteration'. We must inquire what each of 
them is ; and whether * alteration ' is to be identified with 5 
coming-to-be, or whether to these different names there 
correspond two separate processes with distinct natures. 

On this question, indeed, the early philosophers are 
divided. Some of them assert that the so-called ' unqualified 
coming-to-be ' is ' alteration ', while others maintain that 
' alteration ' and coming-to-be are distinct. For those who 
say that the universe is one something (i. e. those who 
generate all things out of one thing) are bound to assert 
that coming-to-be is ' alteration ', and that whatever ' comes- 10 
to-be ' in the proper sense of the term is ' being altered ' : 
but those who make the matter of things more than one 
must distinguish coming-to-be from 'alteration'. To this 
latter class belong Empedokles, Anaxagoras, and Leukippos. 
And yet Anaxagoras himself failed to understand his own 
utterance. He says, at all events, that coming-to-be and 
passing-away are the same as ' being altered ' : ^ yet, in 15 
common with other thinkers, he affirms that the elements 
are many. Thus Empedokles holds that the corporeal 
elements are four, while all the elements — including those 
which initiate movement— are six in number ; whereas 

^ Cf. fr. 17 (Diels, pp. 320-1). 

645.18 B 



314* DE GENERATIONE ET CORRUPTIONE 

Anaxagoras agrees with Leuklppos and Demokritos that 
the elements are infinite. 

(Anaxagoras posits as elements the ' homoeomeries ', viz. 

20 bone, flesh, marrow, and everything else which is such that 
part and whole are the same in name and nature ; while 
Demokritos and Leukippos say that there are indivisible 
bodies, infinite both in number and in the varieties of their 
shapes, of which everything else is composed — the com- 
pounds differing one from another according to the shapes, 
* positions ', and ' groupings ' of their constituents.) 

25 For the views of the school of Anaxagoras seem diamet- 
rically opposed to those of the followers of Empedokles. 
Empedokles says that Fire, Water, Air, and Earth are four 
elements, and are thus 'simple' rather than flesh, bone, and 
bodies which, like these, are ' homoeomeries '. But the 
followers of Anaxagoras regard the ' homoeomeries ' as 
' simple ' and elements, whilst they affirm that Earth, Fire, 
Water, and Air are composite ; for each of these is (accord- 
314^ ing to them) a ' common seminary ' of all the ' homoeo- 
meries'.^ 

Those, then, who construct all things out of a single 
element, must maintain that coming-to-be and passing- 
away are ' alteration '. For they must affirm that the under- 
lying something always remains identical and one ; and 
change of such a substratum is what we call ' altering '. 
Those, on the other hand, who make the ultimate kinds of 
5 things more than one, must maintain that ' alteration ' is 
distinct from coming-to-be : for coming-to-be and passing- 
away result from the consilience and the dissolution of the 
many kinds. That is why Empedokles too ^ uses language 
to this effect, when he says ' There is no coming-to-be of 
anything, but only a mingling and a divorce of what has 
been mingled '.'^ Thus it is clear (i) that to describe coming- 

^ Aristotle's point (from 314^11 to 314''!) is that Anaxagoras, 
Empedokles, Leukippos, and Demokritos are all pluralists, and there- 
fore logically bound (whatever they may say) to distinguish coming-to- 
be and 'alteration'. They are all pluralists, though their theories 
dififer, and though the theory of Anaxagoras is actually 'contrary' to 
that of P^mpedokles. 

2 i. e. as well as Anaxagoras : cf. above, 314^ 13-1 5. 

^ Cf. fr. 8 (Uiels, p. 175), and the paraphrase in MXG 975^36-^16. 



BOOK I. I 314^ 

to-be and passing-away in these terms is in accordance 
with their fundamental assumption, and (ii) that they do in 10 
fact so describe them : nevertheless, they too ^ must recog- 
nize ' alteration ' as a fact distinct from coming-to-be, 
though it is impossible for them to do so consistently with 
what they say. 

That we are right in this criticism is easy to perceive. 
For ' alteration ' is a fact of observation. While the sub- 
stance of the thing remains unchanged, we see it ' altering ' 
just as we see in it the changes of magnitude called ' growth ' 15 
and ' diminution '. Nevertheless, the statements of those 
who posit more ' original reals ' than one make ' alteration ' 
impossible. For ' alteration ', as we assert, takes place in 
respect to certain qualities : and these qualities (I mean, 
e. g., hot-cold, white-black, dry-moist, soft-hard, and so 
forth) are, all of them, differences characterizing the 20 
' elements '. The actual words of Empedokles may be 
quoted in illustration — 

The sun everywhere bright to see, and hot ; 
The rain everywhere dark and cold ; ^ 

and he distinctively characterizes his remaining elements in 

a similar manner. Since, therefore, it is not possible ^ for 

Fire to become Water, or Water to become Earth, neither 

will it be possible for anything white to become black, or 

anything soft to become hard ; and the same argument 25 

applies to all the other qualities. Yet this is what 'alteration' 

essentially is. 

It follows, as an obvious corollary, that a single matter 

must always be assumed as underlying the contrary ' poles ' 

of any change — whether change of place, or growth and 

diminution, or ' alteration ' ; further, that the being of this 

matter and the being of ' alteration ' stand and fall together. 

For if the change is ' alteration ', then the substraittm is 315* 

a single element ; i. e. all things which admit of change 

into one another have a single matter. And, conversely, if 

the substratum of the changing things is one, there is 

* alteration '. 

^ i.e. as well as ordinary people : cf. '^ 13 ff. 
2 Cf. fr. 21, 11. 3 and 5 (Diels, p. 180). 
^ i. e. according to Empedokles. 

B % 



315^ DE GENERATIONE ET CORRUPTIONE 

Empedokles, indeed, seems to contradict his own state- 
5 ments as well as the observed facts. For he denies that any 
one of his elements comes-to-be out of any other, insisting 
on the contrary that they are the things out of which every- 
thing else comes-to-be ; and yet (having brought the 
entirety of existing things, except Strife, together into one) 
he maintains, simultaneously with this denial, that each 
thing once more comes-to-be out of the One. Hence it was 
clearly out of a One that this came-to-be Water, and that 

10 Fire, various portions of it being separated off by certain 
characteristic differences or qualities — as indeed he calls the 
sun ' white and hot ', and the earth ' heavy and hard \ If, 
therefore, these characteristic differences be taken away (for 
they can be taken away, since they came-to-be), it will 
clearly be inevitable for Earth to come-to-be out of Water 
and Water out of Earth, and for each of the other elements 
to undergo a similar transformation — not only then} but 

15 also now — if, and because, they change their qualities. And, 
to judge by what he says, the qualities are such that they 
can be ' attached ' to things and can again be * separated ' 
from them, especially since Strife and Love are still fighting 
with one another for the mastery. It was owing to this 
same conflict that the elements were generated from a One 
at the former period. I say ' generated \ for presumably 
Fire, Earth, and Water had no distinctive existence at all 
while merged in one. 

There is another obscurity in the theory of Empedokles. 

20 Are we to regard the One as his ' original real ' ? Or is it 
the Many — i. e. Fire and Earth, and the bodies co-ordinate 
with these ? For the One is an ' element ' in so far as it 
underlies the process as matter — as that out of which Earth 
and Fire conie-to-be through a change of qualities due to 
'the motion'.^ On the other hand, in so far as the One 
results from composition (by a consilience of the Many), 
whereas they result from disintegration ^ the Many are more 

25 ' elementary ' than the One, and prior to it in their nature. 

^ i. e. at the period when Empedokles himself appears to recognize 
that his 'elements' come-to-be. 

^ i.e. the motion of dissociation initiated by Strife. 



BOOK I. 2 315^ 

2 We have therefore to discuss the whole subject of ^un- 
qualified ' coming-to-be and passing-away ; we have to 
inquire whether these changes do or do not occur and, if 
they occur, to explain the precise conditions of their occur- 
rence. We must also discuss the remaining forms of change, 
viz. growth and 'alteration '. For though, no doubt, Plato 
investigated the conditions under which things come-to-be 
and pass-away, he confined his inquiry to these changes ; 3° 
and he discussed wo'Call coming-to-be. but only that of the 
elements. He asked no questions as to how flesh or bones, 
or any of the other similar compound things, come-to-be ; 
nor again did he examine the conditions under which 
' alteration ' or growth are attributable to things. 

A similar criticism applies to all our predecessors with 
the single exception of Demokritos. Not one of them pene- 35 
trated below the surface or made a thorough examination 
of a single one of the problems. Demokritos. however, 
does seem not only to have thought carefully about all the 
problems, but also to be distinguished from the outset by 3^5^ 
his method. For, as we are saying, none of the other philo- 
sophers made any definite statement about growth, except 
such as any amateur might have made. They said that 
things grow 'by the accession of like to like', but they did 
not proceed to explain the manner of this accession. Nor 
did they give any account of ' combination ' : and they neg- 
lected almost every single one of the remaining problems, 
offering no explanation, e. g., of '' action ' or ' passion ' — how 5 
in physical actions one thing acts and the other undergoes 
action. Demokritos and Leukippos. however, postulate the 
'figures', and make 'alteration' and coming-to-be result 
from them. They explain coming-to-be and passing- away 
by their 'dissociation' and 'association', but 'alteration' 
by their ' grouping ' and ' position '. And since they thought 
that the truth lay in the appearance, and the appearances 10 
are conflicting and infinitely many, they made the ' figures ' 
infinite in number.^ Hence — owing to the changes of the 
compound — tJie same thing seems different and conflicting 
to different people : it is 'transposed' b}^ a small additional 
^ And in variety of shape also: cf. above, 314^^22-3. 



315^ DE GENERATIONE ET CORRUPTIONE 

ingredient, and appears utterly other by the * transposition ' 

15 of a single constituent. For Tragedy and Comedy are both 
composed of the same letters. 

Since almost all our predecessors .think (i) that coming- 
to-be is distinct from 'alteration', and (ii) that, whereas 
things ' alter ' by change of their qualities, it is by ' asso- 
ciation ' and * dissociation ' that they come-to-be and pass- 
away, we must concentrate our attention on these theses. 
For they lead to many perplexing and well-grounded 

20 dilemmas. If, on the one hand, coming-to-be is ' association ', 
many impossible consequences result : and yet there are 
other arguments, not easy to unravel, which force the con- 
clusion upon us that coming-to-be cannot possibly be any- 
thing else. If, on the other hand, coming-to-be is not 
' association ', either there is no such- thing as coming-to-be 
at all or it is ' alteration ' : or else ^ we must endeavour to 
unravel this dilemma too — and a stubborn one we shall 
find it. 

25 The fundamental question, in dealing with all these diffi- 
culties, is this: 'Do things come-to-be and "alter" and 
grow, and undergo the contrary changes, because the 
primary " reals " are indivisible magnitudes ? Or is no mag- 
nitude indivisible ? ' For the answer we give to this question 
makes the greatest difference. And again, if the primary 

30 ' reals ' are indivisible magnitudes, are these bodies^ as Demo- 
krltos and Leuklppos maintain ? Or are they planes, as is 
asserted in the Timaeus} 

To resolve bodies into planes and no further — this, as 
we have also remarked elsewhere,^ is In Itself a paradox. 
Hence there Is more to be said for the view that there are 
indivisible bodies. Yet even these Involve much of paradox. 
Still, as we have said. It Is possible to construct ' alteration ' 

35 and coming-to-be with them, if one ' transposes ' the same 

075^ by 'turning' and ' Intcrcontact ', and by ' the varieties of the 

figures ', as Demokrltos docs. (His denial of the reality of 

colour is a corollary from this position : for, according to 

^ i.e. if we still wish to maintain that coming-to-be (though it 
actually occurs and is distinct from 'alteration ') is not * association'. 
* Cf. e. g. de Caelo 299"' 6- 1 1 . 



BOOK I. 2 316^ 

him, things get coloured by ' turning ' of the ' figures '.) But 
the possibility of such a construction no longer exists for 
those who divide bodies into planes. For nothing except 
solids results from putting planes together : they do not 
even attempt to generate any quality from them. 

Lack of experience diminishes our power of taking 5 
a comprehensive view of the admitted facts. Hence those 
who dwell in intimate association with nature and its 
phenomena grow more and more able to formulate, as the 
foundations of their theories, principles such as to admit of 
a wide and coherent development : while those whom 
devotion to abstract discussions has rendered unobservant 
of the facts are too ready to dogmatize on the basis of a few 10 
observations. The rival treatments of the subject now 
before us will serve to illustrate how great is the difference 
between a ' scientific ' and a ' dialectical ' method of in- 
quiry. For, whereas the Platonists argue that there must 
be atomic magnitudes ' because otherwise " The Triangle " 
will be more than one ', Demokritos would appear to have 
been convinced by arguments appropriate to the subject, 
i.e. drawn from the science of nature. Our meaning will 
become clear as we proceed. 

For to suppose that a body (i. e. a magnitude) is divisible 15 
through and through, and that this division is possible, 
involves a difficulty. What will there be in the body which 
escapes the division ? 

If it is divisible through and through, and if this division 
is possible, then it might be^ at one and the same moment, 
divided through and through, even though the dividings 
had not been effected simultaneously : and the actual 
occurrence of this result would involve no impossibility. 
Hence the same principle will apply whenever a body is 20 
by nature divisible through and through, whether by 
bisection,^ or generally by any method whatever : nothing 
impossible will have resulted if it has actually been divided — 
not even if it has been divided into innumerable parts, 
themselves divided innumerable times. Nothing impossible 

^ i. e. by progressive bisection ad i7ifinitum. 



3i6^ DE GENERATIONE ET CORRUPTIONE 

will have resulted, though perhaps nobody in fact could so 
divide it. 

Since, therefore, the body is divisible through and 
through, let it have been divided. What, then, will remain ? 
A magnitude ? No : that is impossible, since then there 

25 will be something not divided, whereas ex hypothesi the 
body was divisible through and through. But if it be 
admitted that neither a body nor a magnitude will remain, 
and yet division ^ is to take place, the constituents of the 
body will either be points (i.e. without magnitude) or 
absolutely nothing. If its constituents are nothings, then 
it might both come-to-be out of nothings and exist as 
a composite of nothings : and thus presumably the whole 
body will be nothing but an appearance. But if it consists 

30 of points, a similar absurdity will result : it will not possess 
any magnitude. For when the points were in contact and 
coincided to form a single magnitude, they did not make 
the whole any bigger (since, when the body was divided 
into two or more*parts, the whole ^ was not a bit smaller or 
bigger than it was before the division) : hence, even if all 
the points ^ be put together, they will not make any 
magnitude. 

But suppose that, as the body is being divided, a minute 
316^ section — a piece of sawdust, as it were — is extracted^ and 
that in this sense a body 'comes away' from the magnitude, 
evading the division. Even then the same ^ argument 
applies. For in what sense is that section divisible ? But if 
what ' came away ' was not a body but a separable form or 
quality, and if the magnitude is * points or contacts thus 
5 qualified ' : it is paradoxical that a magnitude should 
consist of elements which are not magnitudes. Moreover, 
zvhere will the points be ? And are they motionless or 
moving? And every contact is always a contact of two 
somethings, i. e. there is always something besides the 
contact or the division or the point. 

■■ i.e.' through and through * division. 
^ i. e. the sum of the now separated parts. 

' i. e. all the points into which the body has been dissolved by the 
* through and tlirough ' division. 
^ Cf. above, 316-^24-5. 



BOOK I. 2 316^ 

These, then, are the difficulties resulting from the 
supposition that any and every body, whatever its size, 
is divisible through and through. There is, besides, this 
further consideration. If, having divided a piece of wood 10 
or anything else, I put it together, it is again equal to what 
it was, and is one. Clearly this is so, whatever the point 
at which I cut the wood. The wood, therefore, has been 
divided potentially through and through. What, then, is 
there in the wood besides the division? For even if we 
suppose there is some quality, yet how is the wood 
dissolved into such constituents ^ and how does it come-to- 
be out of them ? Or how are such constituents separated so 
as to exist apart from one another ? 

Since, therefore, it is impossible for magnitudes to 15 
consist of contacts or points, there must be indivisible 
bodies and magnitudes. Yet, if we do postulate the latter, 
we are confronted with equally impossible consequences, 
which we have examined in other works.^ But we must try 
to disentangle these perplexities, and must therefore formu- 
late the whole problem over again. 

On the one hand, then, it is in no way paradoxical that 20 
every perceptible body should be indivisible as well as 
divisible at any and every point. For the second predicate 
will attach to it potentially^ but the first actually. On the 
other hand, it would seem to be impossible for a body to 
be, even potentially, divisible at all points simultaneously. 
For if it were possible, then it might actually occur, with 
the result, not that the body would simultaneously be 
actually both (indivisible and divided), but that it would 
be simultaneously divided at any and every point. Con- 25 . 
sequently, nothing will remain and the body will have 
passed-away into what is incorporeal ; and so it might 
come-to-be again either out of points or absolutely out of 
nothing. And how is that possible ? 

But now it is obvious that a body is in fact divided into 
separable magnitudes which are smaller at each division — 
into magnitudes which fall apart from one another and are 

^ i. e. points-of-division and quality. 

^ Cf. Physics 231^ 21 ff. ; de Caelo 303«^ 3 ff. ; de Lin. Insec. 969^' 29 ff. 



3i6^ DE GENERATIONE ET CORRUPTIONE 

actually separated. Hence (it is urged) the process of 
30 dividing a body part by part is not a ' breaking up ' which 
could continue ad infinitum ; nor can a body be simul- 
_ taneously divided at every point, for that is not possible ; 
but there is a limit, be3^ond which the ' breaking up ' can- 
not proceed. The necessary consequence — especially if 
coming-to-be and passing-away are to take place by 
' association ' and ' dissociation ' respectively — is that a 
body ^ must contain atomic magnitudes which are invisible. 
317^ Such is the argument which is believed to establish the 
necessity of atomic magnitudes : we must now show that it 
conceals a faulty inference, and exactly where it conceals it. 
For, since point is not 'immediately-next' to point, 
magnitudes are ' divisible through and through ' in one 
sense, and yet not in another. When, however, it is ad- 
5 mitted that a magnitude is ' divisible through and through ', 
it is thought there is a point not only anywhere, but also 
everywhere, in it : hence it is supposed to follow, from the 
admission, that the magnitude must be divided away into 
nothing. For — it is supposed — there is a point everywhere 
within it, so that it consists either of contacts or of points. 
But it is only in one seiise that the magnitude is ' divisible 
through and through', viz. in so far as there is one point 
anywhere within it and all its points are everywhere within it 
if you take them singly one by one. But there are not 
more points than one anywhere within it, for the points are 
not ' consecutive ' : hence it is not simultaneously * divisible 
10 through and through '. For if it were, then, if it be 
divisible at its centre, it will be divisible also at a point 
'immediately-next' to its centre. But it is not so divisible: 
for position is not 'immediately-next' to position, nor point 
to point — in other words, division is not ' immediatel}*- 
next' to division, nor composition to composition. 

Hence there arc both 'association' and 'dissociation', 

though neither {a) into, and out of, atomic magnitudes (for 

15 that involves many impossibilities), nor [b) so that division 

takes place through and through — for this would have 

resulted only if point had been ' immediately-next ' to 

^ i.e. every perceptible body : cf. above, 316^21, 



BOOK I. 2 317' 

point: but 'dissociation' takes place into small (i.e. re- 
latively small) parts, and * association ' takes place out of 
relatively small parts. 

It is wrong, however, to suppose, as some assert, that 
coming-to-be and passing-away in the unqualified and 
complete sense are distinctively defined by ' association ' 
and ' dissociation ', while the change that takes place in 
what is continuous is ' alteration '. On the contrary, this is 
where the whole error lies. For unqualified coming-to-be 20 
and pajssing-away are not effected by * association ' and 
' dissociation '. They take place when a thing changes, 
from this to that, as a whole. But the philosophers we 
are criticizing^ suppose that all such change^ is ^alteration ' : 
whereas in fact there is a difference. For in that which 
underlies the change there is a factor corresponding to the 
definition - and there is a material factor. When, then, the 25 
change is in these constitutive factors, there will be coming- 
to-be or passing-away : but when it is in the thing's 
qualities, i. e. a change of the thing per accidens, there will 
be ' alteration '. 

' Dissociation ' and^ ' association ' affect the thing's sus- 
ceptibility to passing-away. For if water has first been 
' dissociated ' into smallish drops, air comes-to-be out of it 
more quickly : while, if drops of water have first been 
' associated ', air comes-to-be more slowly. Our doctrine 
will become clearer in the sequel.^ Meantime, so much 30 
may be taken as established — viz. that coming-to-be 
cannot be * association ', at least not the kind of ' associa- 
tion ' some philosophers assert it to be. 

3 Now that we have established the preceding distinctions, 
we must first* consider whether there is anything which 
comes-to-be and passes-away in the unqualified sense : or 
whether nothing comes-to-be in this strict sense, but 
everything always comes-to-be something and 02it of some- 
thing — I mean, e. g., comes-to-be-healthy out of being-ill 35 

^ i. e. all change ' in what is continuous '. 

'^ i.e. a 'formal' factor. 

^ Cf. 328^23ff. 

* The second main topic of investigation is formulated below, 



317^ DE GENERATIONE ET CORRUPTIONE 

and ill out of being-healthy, comes-to-be-small out of being- 

317^ big and big out of being-small, and so on in every other 

instance. For if there is to be coming-to-be without 

. qualification, ' something ' must — without qualification — 

* come-to-be out of not-being ', so that it would be true to 
say that ' not-being is an attribute of some things '. For 
qualified coming-to-be is a process out of qualified not-being 

5 (e. g. out of not- white or not-beautiful), but unqualified 
coming-to-be is a process out of tmqualified not-being. 

Now ' unqualified' means either (i) the primary predica- 
tion within each Category, or (ii) the universal, i. e. the all- 
comprehensive, predication. Hence, if ' unqualified not- 
being ' means the ne^tion of ' being ' in the sense of the 
primary term of the Category in question, we shall have, in 

* unqualified coming-to-be ', a coming-to-be of a substance 
out of not-substance. But that which is not a substance or 
a ' this ' clearly cannot possess predicates drawn from any 

10 of the other Categories either — e.g. we cannot attribute to 
it any quality, quantity, or position. Otherwise, properties 
would admit of existence in separation from substances. 
If, on the other hand, ' unqualified not-being' means 'what 
is not in any sense at all ', it will be a universal negation of 
all forms of being, so that what comes-to-be will have to 
come-to-be out of nothing. 

Although we have dealt with these problems at greater 

length in another work,^ where we have set forth the 

difficulties and established the distinguishing definitions, the 

15 following concise restatement of our results must here be 

offered : — 

In one sense things come-to-be out of that which has no 
' being ' without qualification : yet in another sense they 
come-to-be always out of ' what is '. For coming-to-be 
necessarily implies the pre-existence of something which 
potentially ' is ', but acttially ' is not ' ; and this something is 
spoken .of both as ' being ' and as ' not-being '. 

These distinctions may be taken as established : but even 
then it is extraordinarily difficult to see how there can be 
'unqualified coming-to-be' (whether we suppose it to occur 
* Physics A. 6-9. 



BOOK I. 3 317 

out of what potentially 'is \ or in some other way), and we 20 
must recall this problem for further examination. For the 
question might be raised whether substance (i. e. the ' this ') 
comes-to-be at all. Is it not rather the 'such', the -'so great', 
or the ' somewhere ', which comes-to-be ? And the same 
question might be raised about ' passing-away ' also. For 
if a substantial thing comes-to-be, it is clear that there will 
' be ' (not actually, but potentially) a substance, out of 
which its coming-to-be will proceed and into which the 
thing that is passing-away will necessarily change. Then will 25 
any predicate belonging to the remaining Categories attach 
actually to this presupposed substance ? In other words, 
will that which is only potentially a ' this ' (which only 
potentially is)^ while without the qualification ' potentially ' 
it is not a ' this ' (i. e. is not), possess, e. g., any determinate 
size or quality or position ? For (i) if it possesses none of 
these determinations actually, but all of them only 
potentially, the result is first that a being, which is not 
a determinate being, is capable of separate existence; and 
ill addition that coming-to-be proceeds out of nothing pre- 
existing — a thesis which, more than any other, preoccupied 30 
and alarmed the earliest philosophers. On the other 
hand (ii) if, although it is not a ' this somewhat ' or a sub- 
stante, it is to possess some of the remaining determinations 
quoted above, then (as we said) ^ properties will be 
separable from substances. 

We must therefore concentrate all our powers on the 
discussion of these difficulties and on the solution of a 
further question — viz. What is the cause of the perpetuity 35 
of coming-to-be? Why is there always unqualified,^ as 
well 2.S partial,^ coming-to-be? 

' Cause ' in this connexion has two senses. It means 318' 
(i) the source from which, as we say, the process 'originates', 
and (ii) the matter. It is the material cause that we have 
here to state,. For, as to the other cause, we have already 



^ Cf. above, 317^10-11. 

"^ 'Unqualified coming-to-be' = substantial change. 
^ ' Partial ' = ' qualified ' coming-to-be, i. e. change of quality, 
quantity, or place. 



3i8^ DE GENERATIONE ET CORRUPTIONE 

explained (in our treatise on Motion^) that it involves 
(a) something immovable through all time and (b) some- 

5 thing always being moved. And the accurate treatment of 
- the first of these — of the immovable 'originative source' — 
belongs to the province of the other, or ' prior ', philo- 
sophy : ^ while as regards ' that which sets everything else 
in motion by being itself continuously moved ', we shall 
have to explain later ^ which amongst the so-called 'specific' 
causes exhibits this character. But at present we are to 
state the material cause — the cause classed under the head 

10 of matter — to which it is due that passing-away and com- 
ing-to-be never fail to occur in Nature. For perhaps, if we 
succeed in clearing up this question, it will simultaneously 
become clear what account we ought to give of that which 
perplexed us just now, i.e. of wiqi/alified passing-cLway and 
coming-to-be. 

Our new question too — viz. * what is the cause of the 
unbroken continuity of coming-to-be ? ' — is sufficiently per- 
plexing, if in fact what passes-away vanishes into ' what is 

15 not ' and ' what is not ' is nothing (since ' what is not ' is 
neither a thing, nor possessed of a quality or quantity, nor 
in any place). If, then, some one of the things ' which are ' 
is constantly disappearing, why has not the whole of * what 
is ' been used up long ago and vanished away — assuming of 
course that the material of all the several comings-to-be 
was finite? For, presumably, the unfailing continuity of 
coming-to-be cannot be attributed to the infinity of the 

20 material. That is impossible, for nothing is actually infinite. 
A thing is infinite only potentially, i. e. the dividing of it 
can continue indefinitely : so that we should have to sup- 
pose there is only one kind of coming-to-be in the world — 
viz. one which never fails, because it is such that what 
comes-to-be is on each successive occasion smaller than 
before. But in fact this is not what we see occurring. 

25 Why, then^ is this form of change necessarily ceaseless ? 
Is it because the passing-away of ^/iis is a coming-to-be of 

^ Physics e. 3ff., especially 258^' 10 ff. 

^ i. e. TTpoiTT] c/jiXocro^ia or ^eoXoyiK/'y. 

3 Cf. below, II. 10. 



i 



BOOK I. 3 318^ 

something else^ and the coming-to-be of this a passing-away 
of something else ? 

The cause implied in this sokition ^ must no doubt 
be considered adequate to account for coming-to-be and 
passing-away in their general character as they occur in all 
existing things alike. Yet, if the same process is a coming- 30 
to-be of this but a passing-away of that^ and a passing-away 
of this but a coming-to-be of that^ why are some things said 
to come-to-be and pass-away without qualification, but 
others only with a qualification ? 

This distinction must be investigated once more/ for it 
demands some explanation. (It is applied in a twofold 
manner.) ^ For (i) we say ' it is now passing-away ' without 
qualification^ and not merely ' this is passing-away ' : * and 
we call this change ' coming-to-be ', and that ' passing- 
away ', without qualification. And (ii) so-and-so ' comes-to- 
be-something ', but does not ' come-to-be ' without quali- 
fication; for we say that the student * comes-to-be-learned', 35 
not ' comes-to-be ' without quahfication. 

(i) Now we often divide terms into those which signify 318^ 
a * this somewhat ' and those which do not. And (the first 
form of) ^ the distinction, which we are investigating, results 
from a similar division of terms : for it makes a difference 
into what the changing thing changes. Perhaps, e.g., the 
passage into Fire is -'coming-to-be' unqualified, but 'passing- 
away-of-something ' (e. g. of Earth) : whilst the coming-to- 
be of Earth is qualified (not unqualified) ' coming-to-be ', 5 
though unqualified ' passing-away ' (e. g. of Fire). This 
would be the case on the theory set forth in Parmenides : ^ 
for he says that the things into which change takes place 
are two, and he asserts that these two, viz. what is and 
what is not, are Fire and Earth. Whether we postulate 

^ i.e. the material cause, in the sense of -pcor?; vXtj: cf. 319^18-22. 

- ' Once more ' : for it was from this same peculiarity of linguistic 
usage that Aristotle started (^ly^^^ff.) to establish the being of dTvXrj 
yevecTLS. 

^ I have inserted this sentence in view of what follows : cf. 319* 3-1 1. 

^ i.e. not merely ' t/n's is passing-away and //lat is coming-to-be*. 

^ See note 3. 

^ The theory is put forward by Parmenides (fr. 8, 11, 5 iff.; Diels, 
pp. 121-2) as the prevalent, but erroneous, view. See Burnet, 
§§ 90,91- 



3i8^ DE GENERATIONE ET CORRUPTIONE 

these,^ or other things of a similar kind, makes no difference. 
For we are trying to discover not what undergoes these 
changes, but what is their characteristic manner. The 
I© passage, then, into what ' is ' not except with a quaHfication 
is unquaHfied passing-away, while the passage into what 
' is ' without qualification is unqualified coming-to-be. 
Hence whatever the contrasted ' poles ' of the changes may 
be — whether Fire and Earth, or some other couple — the 
one of them will be ' a being ' and the other ' a not-being '.^ 
We have thus stated one characteristic manner in which 
tmqim/ijied will be distinguished from ^^(^///?^<^ coming-to-be 
and passing-away: but they are also distinguished according 
to the special nature of the material of the changing thing. 

15 For a material, whose constitutive differences signify more 
a * this somewhat ', is itself more * substantial ' or ' real ' : 
while a material, whose constitutive differences signify pri- 
vation, is * not real '. (Suppose, e. g., that ' the hot ' is a 
positive predication, i.e. a 'form', whereas ' cold' is a priva- 
tion; and that Earth and Fire differ from one another by 
these constitutive differences.) 

The opinion, however, which most people are inclined to 
prefer, is that the distinction ^ depends upon the difference 
between ' the perceptible ' and ' the imperceptible '. Thus, 

20 when there is a change into perceptible material, people say 
there is ' coming-to-be ' ; but when there is a change into 
invisible material, they call it ' passing-away '. For they 
distinguish ' what is ' and ' what is not ' by their perceiving 
and not-perceiving, just as what is knowable Ms' and what 
is unknowable ' is not ' — perception on their view having 

25 the force of knowledge. Hence, just as they deem them- 
selves to live and to ' be ' in virtue of their perceiving or 
their capacity to perceive, so too they deem the things to 
'be' ^ua perceived or perceptible — and in this they are in a 
sense on the track of the truth, though what they actually 
say is not true. 

^ sc. as the things into which the unqualified changes take place — 
as the contrasted ' poles ' of unqualified yeveais and (f)6opd, 

^ i.e. one will be 'a positive real' and the other 'a negative 
something '. 

^ sc. between the unqualified and the qualified changes. 



BOOK I. 3 318^ 

Thus unqualified coming-to-be and passing-away turn out 
to be different according to common opinion from what 
they are in truth.^ For Wind and Air are in truth more 
real — more a * this somewhat' or a ' form ' — than Earth. 
But they are less real to perception — which explains why 
things are commonly said to ' pass-away ' without qualifica- 30 
tion when they change into Wind and Air, and to ' come-to- 
be'^ when they change into what is tangible, i.e. into Earth. 

We have now explained why there is * unqualified coming- 
to-be ' (though it is a passing-away-of-something) and ' un- 
qualified passing-away ' (though, it is a coming-to-be-of- 
something). For this distinction of appellation depends upon 35 
a difference in the material out of which, and into which, 
the changes are effected. It depends either upon whether 
the material is or is not ' substantial ', or upon whether it is 3^9' 
more or less ' substantial ', or upon whether it is more or 
less perceptible. 

(ii) But why are some things said to ' come-to-be ' with- 
out qualification, and others only to 'come-to-be-so-and-so', 
in cases different from the one we have been considering 
where two things come-to-be reciprocally out of one another? 
For at present we have explained no more than this: — why, 5 
when two things change reciprocally into one another, we 
do not attribute coming-to-be and passing-away uniformly 
to them both, although every coming-to-be is a passing- 
away of something else and every passing-away some other 
thing's coming-to-be. But the question subsequently formu- 
lated involves a different problem — viz. why, although the 
learning thing is said to ' come-to-be-learned ' but not to 10 
* come-to-be' without qualification, yet the growing thing 
is said to ' come-to-be '. 

The distinction here turns upon the difference of the 
Categories. For some things signify a this somezvhat^ others 
a such^ and others a so-much. Those things, then, which 
do not signify substance, are not said to ' come-to-be ' with- 
out qualification, but only to ' come-to-be-so-and-so '. 

^ ',In truth', i.e. according to Aristotle's own view which he has 
just stated (above, 318^ 14-18). 
^ sc. without qualification. 

645-18 C 



319^ DE GENERATIOxNE ET CORRUPTIONE 

Nevertheless, in all changing things alike, we speak of 

15 'coming-to-be'^ when the thing comes-to-be something in 
oiie'^ of the two Columns — e.g. in Substance, if it comes-to- 

- be Fire but not if it comes-to-be Earth ; and in Quality, if 
it comes-to-be learned but not when it comes-to-be ignorant. 
We have explained why some things come-to-be without 
qualification, but not others — both in general, and also 
when the changing things are substances and nothing else ; 
and we have stated that the siLbsti^atmn is the material cause 
of the continuous occurrence of coming-to-be, because it is 

20 such as to change from contrary to contrary and because, 
in substances, the coming-to-be of one thing is always 
a passing-away of another, and the passing-away of one 
thing is always another's coming-to-be. But there is no 
need even to discuss the other question we liaised — viz. 
why coming-to-be continues though things are constantly 
being destroyed.^ For just as people speak of 'a passing- 
away ' without qualification when a thing has passed into 
what is imperceptible and what in that sense ' is not ', so 

25 also they speak of ' a coming-to-be out of a not-being ' when 
a thing emerges from an imperceptible. Whether, there- 
fore, the substratimi is or is not something, what comes-to- 
be emerges out of a ' not-being ' : * so that a thing ' comes- 
to-be out of a not-being ' just as much as it ' passes-away 
into what is not'. Hence it is reasonable enough that 
coming-to-be should never fail. For coming-to-be is a 
passing-away of ' what is not ' and passing-away is a coming- 
to-be of ' what is not '.^ 

But what about that which ' is ' not except with a quali- 

30 fication ? ^ Is it one of the two contrary poles of the change 
— e. g. is Earth (i. e. the heavy) a ' not-being ', but Fire (i. e. 

^ i. e. without qualification. 

^ i. e. in the Column containing the positive terms : cf. above, 
318^14-18. 

^ Cf. above, 318=^ 13-23. 

^ A 'not-being' in the popular sense of the term, i.e. an 'imper- 
ceptible '. The imperceptibility of the material is irrelevant to the 
question of its reality. 

•' ' what is not ' = what is imperceptible. 

^ The matter of substantial change, according to Aristotle's own 
theory, is />ir/ *)v aTrXwy — i.e. it is not, unless you qualify ' is' and say it 
'is-potentially '. Cf. above, 317^15-18. 



BOOK I. 3 319^ 

the light) a 'being'? Or, on the contrary, does 'what is' 
include Earth as well as Fire, whereas ' what is not ' is matter 
— the matter of Earth and Fire alike ? And again, is the 
matter of each different ? Or is it the same, since otherwise 
they would not come-to-be reciprocally out of one another, 319^ 
i. e. contraries out of contraries ? For these things — Fire, 
Earth, Water, Air — are characterized by ' the contraries \^ 

Perhaps the solution is that their matter is in one sense 
the same, but in another sense different. For that which 
underlies them, whatever its nature may be qua underlying 
them, is the same : but its actual being is not the same. So 
4 much, then, on these topics. Next we must state what the 5 
difference is between coming-to-be and 'alteration' — for 
we maintain that these changes are distinct from one 
another. 

Since, then, we must distinguish (a) the substratum^ 
and {b) the property whose nature it is to be predi- 
cated of the substratum ; and since change of each of 10 
these occurs ; there is * alteration ' when the substratum is 
perceptible and persists, but changes in its own properties, 
the properties in question being opposed to one another 
either as contraries or as intermediates. The body, e. g., 
although persisting as the same body, is now healthy and 
now ill ; and the bronze is now spherical and at another 
time angular, and yet remains the same bronze. But 
when nothing perceptible persists in its identity as a sub- 15 
stratum, and the thing changes as a whole (when e.g. the 
seed as a whole is converted into blood, or water into air, 
or air as a whole into water), such an occurrence is no longer 
'alteration'. It is a coming-to-be of one substance and 
a passing-away of the other — especially if the change pro- 
ceeds from an imperceptible something to something 
perceptible (either to touch or to all the senses), as when 
water comes-to-be out of, or passes-away into, air : for air 20 
is pretty well imperceptible. If, however, in such cases, any 
property (being one of a pair of contraries) persists, in the 
thing that has come-to-be, the same as it was in the thing 

^ Cf. below, II. 1-3. 
C 2 



319^ DE GENERATIONE ET CORRUPTIONE 

which has passed-away — if, e.g., when water comes-to-be 
out of air, both are transparent or cold ^ — the second thing, 
into which X\i^ first changes, must not be a property of this 

• persistent identical something. Otherwise the change will 
be ' alteration '. 

25 Suppose, e.g., that the musical man passed-away and an 
unmusical man came-to-be, and that the man persists as 
something identical. Now, if ' musical ness and unmusical- 
ness ' had not been a property^essentially inhering in man, 
these changes would have been a coming-to-be of un- 
musicalness and a passing-away of musicalness : but in fact 
' musicalness and unmusicalness ' are a property of the 
persistent identity, viz. man.^ (Hence, as regards man, 
these changes are ' modifications ' ; though, as regards 

30 musical man and timmtsical man, they are a passing-away 
and a coming-to-be.) Consequently such changes are 
' alteration '.^ 

When the change from contrary to contrary is in quantity, 
it is ' growth and diminution ' ; when it is in place, it is 
'motion'; when it is in property, i.e. in quality, it is 
320^ ' alteration ': but when nothing persists, of which the re- 
sultant is a property (or an ' accident ' in any sense of the 
term), it is ' coming-to-be ', and the converse change is 
' passing-away '. 

' Matter', in the most proper sense of the term, is to be 
identified with the substratum which is receptive of coming- 
to-be and passing-away : but the substratum of the remain- 
ing kinds of change is also, in a certain sense, ' matter ', 
5 because all these substrata are receptive of * contrarieties ' 
of some kind. So much, then, as an answer to the ques- 

^ Aristotle is not saying that water and air are in fact ' cold ', but is 
only quoting a common view in illustration. 

^ I follow Philoponos in transposing vvv . . . vnoixeuovTos (which the 
manuscripts read alter cpBopd in 1. 30) to 1. 28 after rod 8e (f)dopd. 

^ Aristotle's doctrine is: (i) If 'musicalness and unmusicalness' 
were not a property of man, the change in which ' a musical man 
becomes unmusical ' would be a (jidopd of inusicabiess and a ■yeVeo-is 
q{ tuiniusicnhiess. But (ii) since 'musicalness and unmusicalness' are 
a property of man, the change is in fact an 'alteration' of man from 
a state of musicalness to a state of unmusicalness. At the same time, 
(iii) the change is a (fiOnixi of nmsical man and a ycueais of unmusical 
man. 



BOOK I. 4 320* 

tions (i) whether coming-to-be ' is ' or 'is not ' — i. e. what 
are the precise conditions of its occurrence — and (ii) what 
5 * alteration ' is : but we have still to treat of growth.^ We 
must explain (i) wherein growth differs from coming-to-be 
and from ' alteration ', and (ii) what is the process of grow- 
ing and the process of diminishing in each and all of the 10 
things that grov/ and diminish. 

Hence our first question is this : Do these changes differ 
from one another solely because of a difference in their 
respective ' spheres ' ? . In other words, do they differ 
because, while a change from this to that (viz. from poten- 
tial to actual substance) is coming-to-be, a change in the 
sphere of magnitude is growth and one in the sphere of 
quality is ' alteration ' — both growth and * alteration ' being 15 
changes from what is-potentially to what is-actually 
magnitude and quality respectively? Or is there also 
a difference in the manner of the change, since it is evident 
that, whereas neither what is ' altering ' nor what is coming- 
to-be necessarily changes its place, what is growing or 
diminishing changes its spatial position of necessity, though 
in a different manner from that in which the moving thing 
does so ? For that which is being moved changes its place 20 
as a whole : but the growing thing changes its place hke 
a metal that is being beaten, retaining its position as a whole 
while its parts change their places. They change their 
places, but not in the same way as the parts of a revolving 
globe. For the parts of the globe change their places 
while the whole -continues to occupy an equal place: but 
the parts of the growing thing expand over an ever-increas- 
ing place and the parts of the diminishing thing contract 25 
within an ever-diminishing area. 

It is clear, then, that these changes — the changes of that 
which is coming-to-be, of that which is ' altering ', and of 
that which is growing — differ in manner as well as in sphere. 
But how are we to conceive the ' sphere ' of the change 
which is growth and diminution ? The ' sphere ' of growing 
and diminishing is believed to be magnitude. Are we to 

^ Cf. above, 315=^26-28. 



320^ DE GENERATIONE ET CORRUPTIONE 

suppose that body and magnitude come-to-be out of some- 
30 thing which, though potentially magnitude and body, is 
actually incorporeal and devoid of magnitude ? And since 
this description may be understood in two different ways, 
in which of these two ways are we to apply it to the process 
of growth ? Is the matter,^ out of which growth takes 
place, (i) ' separate ' and existing alone by itself, or (ii) 
' separate ' but contained in another body ? ^ 

Perhaps it is impossible for growth to take place in either 
320^^ of these ways. For since the matter ^ is ' separate ', either 
(a) it will occupy no place (as if it were a point), or (d) it 
will be a ' void ', i. e. a non-perceptible body. But the first 
of these alternatives is impossible. For since what comes- 
to-be out of this incorporeal and sizeless something will 
always be ' somewhere ', it too must be * somewhere ' — 
5 either intrinsically or indirectly.* And the second alterna- 
tive necessarily implies that the matter is contained in some 
other body. But if it is to be ' in ' another body and yet 
remains 'separate' in such a way that it is in no sense 
a part of that body (neither a part of its substantial being 
nor an ' accident ' of it), many impossibilities will result. 
It is as if we were to suppose that when, e.g., air comes-to- 
be out of water the process were due not to a change of the 
10 water, but to the matter of the air being ' contained in ' the 
water as in a vessel. This is impossible. For (i) there is 
nothing to prevent an indeterminate number of matters 
being thus ^ contained in ' the water, so that they might 
come-to-be actually an indeterminate quantity of air ; ^ and 
(ii) we do not in fact see air coming-to-be out of water in 
this fashion, viz. withdrawing out of it and leaving it 
unchanged. 

It is therefore better to suppose that in all instances of 

' i.e. the supposed incorporeal and sizeless matter. 

'•^ It is clear from what follows that the incorporeal and sizeless 
matter is assumed to be ' separate ' — to be real independently of body — 
under both alternatives. 

^ i. e. the supposed incorporeal and sizeless matter. 

^ i.e. either as itself occupying a place, or as contained within 
a body which itself occupies a place. 

•^ The original is obscure owing to its extreme compression : I have 
expanded it in accordance with Zabarella's interpretation. 



BOOK I. 5 320 

coming-to-be the matter is inseparable,^ being numerically 
identical and one with the ' containing ' body, though isol- 
able from it by definition. But the same reasons also forbid 
us to regard the matter, out of which the body comes-to-be, 15 
as points or lines. The matter is that of which points and 
lines are limits, and it is something that can never exist 
without quality and without form. 

Now it is no doubt true, as we have also established else- 
where,^ that one thing ' comes-to-be ' (in the unqualified 
sense) out of another thing : and further it is true that the 
efficient cause of its coming-to-be is either (i) an actual 
thing (which is the same as the effect either generically 
— for the efficient cause of the coming-to-be of a hard thing 
is not a hard thing ^ — or specifically^ as e. g. fire is the 20 
efficient cause of the coming-to-be of fire or one man of the 
birth of another), or (ii) an actuality.* Nevertheless, since 
there is also a matter out of which corporeal substance 
itself comes-to-be (corporeal substance, however, already 
characterized as such-and-such a determinate body, for 
there is no such thing as body in general), this same matter 
is also the matter of magnitude and quality — being separ- 
able from these matters by definition, but not separable in 
place unless Qualities are, in their turn^ separable.^ 25 

It is evident, from the preceding ^ development and dis- 
cussion of difficulties, that growth is not a change out of 
something which, though potentially a magnitude, actually 
possesses no magnitude. For, if it were, * the void ' would 
exist in separation ; but we have explained in a former work ^ 
that this is impossible. Moreover, a change of that kind 
is not peculiarly distinctive of growth, but characterizes 

^ ' inseparable ' from the actual body in which it is contained. 

^ Cf. Physics A. 7 ; Metaph. 1032^ 12 fif. 

^ The efficient cause of the coming-to-be of a hard thing (e. g. of ice 
or terra-cotta) is something cold or hot (a freezing wind or a baking 
fire) ; cf. Meteor. 382* 22 ff. Such efficient causes are only generically, 
not specifically, identical with their effects. I have transposed the 
words aKXrjpov yap ovx vtto crKkrjpov yiverai SO as to read them as 
a parenthesis after 6p.oy€vovs in 320^ 19. 

* An ' actuality ' or * form ' : cf. Metaph. 1032^ 25 fif. 

° i.e. unless Qualities or Adjectivals are separable from Substances. 

^ Cf. above, 320^ 27-^ 12. 

' Cf. Physics A. 6-9. 



320*^ DE GENERATIONE ET CORRUPTIONE 

30 coming-to-be as such or in general. For growth is an in- 
crease, and diminution is a lessening, of the magnitude which 
is there already — that, indeed, is why the growing thing 
must possess some magnitude. Hence growth must not 
be regarded as a process from a matter without magnitude 
^ to an actuality of magnitude : for this would be a body's 

coming-to-be rather than its growth. 

We must therefore come to closer quarters with the 
321^ subject of our inquiry. We must ' grapple ' with it (as it 
were) from its beginning, and determine the precise character 
of the growing and diminishing whose causes we are in- 
vestigating. 

It is evident (i) that any and every part of the growing 
thing has increased, and that similarly in diminution every 
part has become smaller : also (ii) that a thing grows by 

5 the accession, and diminishes by the departure, of some- 
thing. Hence it must grow by the accession either 
(a) of something incorporeal or (d) of a body. Now, if 
(a) it grows by the accession of something incorporeal, 
there will exist separate a void : but (as we have stated 
before) ^ it is impossible for a matter of magnitude to exist 
' separate '. If, on the other hand, {b) it grows by the 
accession of a body, there will be two bodies — that which 
grows and that which increases it — in the same place : 
and this too is impossible. 

10 But neither is it open to us to say that growth or 
diminution occurs in the way in which e. g. air is generated 
from water. For, although the volume has then become 
greater, the change will not be growth, but a coming-to-be 
of the one — viz. of that into which the change is taking 
place — and a passing-away of the contrasted body. It is 
not a growth of either. Nothing grows in the process ; 
unless indeed there be something common to both things 

15 (to that which is coming-to-be and to that which passed- 
away), e.g. 'body', and this grows. The water has not 
grown, nor has the air : but the former has passed- 
away and the latter has come-to-be, and — if anything has 
grown — there has been a growth of ' body '. Yet this too 
^ Cf. above, 320^^27 - ^25. 



BOOK I. 5 321^ 

is impossible. For our account of growth must preserve 
the characteristics of that which is growing and diminishing. 
And these characteristics are three : (i) any and every 
part of the gtowing magnitude is made bigger (e. g. if flesh 20 
grows, every particle of the flesh gets bigger), (ii) by the 
accession of something, and (iii) in such a way that the 
growing thing is preserved and persists. For whereas a 
thing does not persist in the processes of unqualified 
coming-to-be or passing-away, that which grows or ' alters ' 
persists in its identity through the ' altering ' and through 
the growing or diminishing, though the quality (in ' altera- 25 
tion ') and the size (in growth) do not remain the same. 
Now if the generation of air from water is to be regarded 
as growth, a thing might grow without the accession (and 
without the persistence) of anything, and diminish without 
the departure of anything — and that which grows need not 
persist. But this characteristic ^ must be preserved : for the 
growth we are discussing has been assumed to be thus 
characterized. 

One might raise a further difficulty. What is ' that which 30 
grows ' ? Is it that to which something is added? If, e.g., 
a man grows in his shin, is it the shin which is greater ^ — 
but not that ' whereby ' he grows, viz. not the food ? Then 
why have not both ' grown ' ? For when A is added to B, 
both A and B are greater, as when you mix wine with 
water; for each ingredient is alike increased in volume. 
Perhaps the explanation is that the substance of the one ^ 
remains unchanged, but the substance of the other (viz. of 35 
the food) does not. For indeed, even in the mixture of wine 321'' 
and water, it is the prevailing ingredient which is said to 
have increased in volume. We say, e. g., that the wine has 
increased, because the whole mixture acts as wine but not 
as water. A similar principle applies also to 'alteration'. 
Flesh is said to have been ' altered ' if, while its character 
and substance remain, some one of its essential properties, 
which was not there before, now qualifies it : on the other 5 

^ viz. the third characteristic — that the growing thing ' persists '. 

^ i. e. has ' grown '. 

^ i. e. the substance of the shin. 



321^ DE GENERATIONE ET CORRUPTIONE 

hand, that ' whereby ' it has been ' altered ' may have under- 
gone no change, though sometimes it too has been affected. 
The altering agent, however, and the originative source of 
the process are in the growing thing and in that which is 
being ' altered ' : for the efficient cause is in these.^ No doubt 
the food, which has come in, may sometimes expand as well 
as the body that has consumed it (that is so, e.g., if, after 
having come in, a food is converted into wind^), but when 
lo it has undergone this change it has passed-away : and the 
efficient cause is not in the food. 

We have now developed the difficulties sufficiently and 
must therefore try to find a solution of the problem. Our 
solution must preserve intact the three characteristics of 
growth — that the growing thing persists, that it grows by 
the accession (and diminishes by the departure) of some- 
thing, and further that every perceptible particle of it has 
15 become either larger or smaller. We must recognize also 
(a) that the growing body is not * void ' and that yet there 
are not two magnitudes in the same place, and (d) that it 
does not grow by the accession of something incorporeal. 

Two preliminary distinctions will prepare us to grasp 
the cause of growth. We must note (i) that the organic 
parts ^ grow by the growth of the tissues * (for every organ 
is composed of these as its constituents) ; and (ii) that flesh, 
20 bone, and every such part ^ — like every other thing which 
has its form immersed in matter — has a twofold nature : for 
the form as well as the matter is called ' flesh ' or ' bone '. 

Now, that any and every part of the tissue qtm form 
should grow — and grow by the accession of something — is 
possible, but not that any and every part of the tissue qua 
matter should do so. For we must think of the tissue after 



' And therefore it is these which are said to grow or to be 'altered'. 

^ Aristotle may be thinking of the conversion of a flatulent food into 
wind. But more probably he has in mind the maintenance and growth 
of the (fxcfivTOu (or avfx(pvT()v) nvevfxa : cf. t/e Spiritu 481^ I ff. 

^ The CJreek is ra di^oMoio/Liep^, i.e. those parts (of the living thing) 
whose texture is not uniform throughout. 

^ The Greek is ra o/xoio/xfp^, i. e. those parts whose texture is uniform 
throughout : cf. above, 314* 19-20. In living things such parts corre- 
spond roughly to 'the tissaes'. 

^ i.e. every ' homoeomerous ' part (or every 'tissue'). 



BOOK I. 5 321* 

the image of flowing water that is measured by one and 25 
the same measure : particle after particle comes-to-be, and 
each successive particle is different.^ And it is in this 
sense that the matter of the flesh grows, some flowing 
out and some flowing in fresh ; not in the sense that fresh 
matter accedes to every particle of it. There is, however, 
an accession to every part of its figure or ' form '. 

That growth has taken place proportionally,^ is more 
manifest in the organic parts — e. g. in the hand. For there 
the fact that the matter is distinct from the form is 30 
more manifest than in flesh, i. e. than in the tissues. That 
is why there is a greater tendency to suppose that a 
corpse still possesses flesh and bone than that it still has 
a hand or an arm. 

Hence in one sense it is true that any and every part 
of the flesh has grown ; but in another sense it is false. 
For there has been an accession to every part of the flesh 
in respect to its form, but not in respect to its matter. 
The whole, however, has become larger. And this increase 35 
is due {a) on* the one hand to the accession of something, 
which is called ' food ' and is said to be ' contrary ' to flesh, 322^ 
but {b) on the other hand to the transformation of this food 
into the same form as that of flesh — ^as if, e.g., 'moist' 
were to accede to ' dry ' and, having acceded, were to be 
transformed and to become ' dry '. For in one sense ' Like 
grows by Like ', but in another sense ' Unlike grows by 
Unlike'. 

One might discuss what must be the character of that 
' whereby ' a thing grows. Clearly it must be potentially 5 
that which is growing — potentially flesh, e.g., if it is flesh 
that is growing. Actually, therefore, it must be ' other ' 
than the growing thing. This ' actual other ', then, has 
passed-away and come-to-be flesh. But it has not been 
transformed into flesh alone by itself (for that would have 

^ I think this clause refers to the matter of the tissue, not to the 
water. In Aristotle's simile, the ' measure ' corresponds to the tissue's 
form, and the ' water' to its matter. The matter is a flux of different 
particles always coming-to-be and passing-away, always ' flowing in 
and out' of the structural plan which is the ' form'. 

^ i. e. by an expansion of all parts of the * form '. 



322^ DE GENERATIONE ET CORRUPTIONE 

been a coming-to-be, not a growth) : on the contrary, it 
is the growing thing which has come-to-be flesh (and grown) ^ 
by the food. In what way, then, has the food been modi- 
fied by the growing thing ? ^ Perhaps we should say that 
it has been ' mixed ' with it, as if one were to pour water 

lo into wine and the wine were able to convert the new 
ingredient into wine. And as fire lays hold of the in- 
flammable,^ so the active principle of growth, dwelling 
in the growing thing (i. e. in that which is actually flesh), 
lays hold of an acceding food which is potentially flesh and 
converts it into actual flesh. The acceding food, therefore, 
must be together with the growing thing : "* for if it were 
apart from it, the change would be a coming-to-be.^ For 

15 it is possible to produce fire by piling logs on to the already 
burning fire. That is ' growth '. But when the logs them- 
selves are set on fire, that is ' coming-to-be '. 

* Quantum-in-general ' does not come-to-be any more 
than 'animal' which is neither man nor any other of the 
specific forms of animal : what ' animal-in-general ' is in 
coming-to-be, that ' quantum-in-general ' is in growth. 
But what does come-to-be in growth is flesh or bone — 
or a hand or arm (i. e. the tissues of these organic parts).^ 

20 Such things come-to-be, then, by the accession not of 
quantified-flesh but of a quantified-something. In so far 
as this acceding food is potentially the double result — 
e.g. is potentially so-much-flesh — it produces growth: for 
it is bound to become actually both so-much and flesh. 
But in so far as it is potentially flesh only, it nourishes : 
for it is thus that ' nutrition ' and ' growth ' difler by their 
definition. That is why a body's ' nutrition ' continues so 

^ All the manuscripts read rjv^rjdrj after toutov in 322^9. We must 
either delete it, or correct it into r^v^rja^v (cf. Philoponos, ed. Vitelli, 
p. 117, 1. 12), or transpose it so as to read it after rovrcd in '^S. I have 
adopted the last alternative in my translation. 

M. e. ' been modified ' so as to be transformed into flesh. 

^ i.e.' lays hold ' of it and converts it into fire. 

* i. e. ' must be together with ' it when this conversion takes place. 

^ i. e. an independent coming-to-be of flesh, not a growth of the 
already existing tissue. 

^ i. e. what comes-to-be in growth is so-much flesh or bone, or 
a hand or arm of such and such a size : not ' quantum-in-general ', 
but a 'quantified-something*. 



BOOK I. 5 322' 

long as it is kept alive (even when it is diminishing), though 
not its ' growth ' ; and why nutrition, though ' the same ' 25 
as growth, is yet different from it in its actual being.' For in 
so far as that which accedes is potentially ' so-much-flesh ' it 
tends to increase flesh : whereas, in so far as it is potentially 
' flesh ' only, it is nourishment. 

The form of which we have spoken ^ is a kind of power 
immersed in matter — a duct, as it were. If, then, a matter 
accedes — a matter, which is potentially a duct and also 30 
potentially possesses determinate quantity — the ducts to 
which it accedes will become bigger. But if it ^ is no 
longer able to act — if it has been weakened by the con- 
tinued influx of matter, just as water, continually mixed 
in greater and greater quantity with wine, in the end makes 
the wine watery and converts it into water — then it will cause 
a diminution of the quantum ; ^ though still the form per- 
sists.^ 



6 (In discussing the causes of coming-to-be)^ we must first 322^ 
investigate the matter, i. e. the so-called ' elements '. We 
must ask whether they really are elements or not, i.e. whether 
each of them is eternal or whether there is a sense in which 
they come-to-be : and, if they do come-to-be, whether all 
of them come-to-be in the same manner, reciprocally out 
of one another, or whether one amongst them is something 

' i.e. the form which grows in every part of itself: cf. above, 
321^22-34. 

^ i. e. this form or power immersed in matter, 

^ i. e. a diminution of the size of the tissue whose form it is. 

* For the reading and interpretation of 322^28-33 see my text 
and commentary. 

^ I have added these words to explain ' first ' : cf. Zabarella, whose 
interpretation I have followed. 



322^ DE GENERATIONE ET CORRUPTIONE 

5 primary. Hence we must begin by explaining certain 
preliminary matters, about which the statements now 
current are vague. 

For all (the pluralist philosophers) — those who generate 
the ' elements ' as well as those who generate the bodies 
that are compounded of the elements — make use of ' dis- 
sociation' and 'association ', and of 'action' and 'passion'. 
Now ' association ' is ' combination ' ; but the precise mean- 
ing of the process we call ' combining ' has not been ex- 
plained. Again, (all the monists make use of ' alteration ' : 

lo but) without an agent and a patient there cannot be ' alter- 
ing' any more than there can be 'dissociating' and 'asso- 
ciating '. For not only those who postulate a plurality of 
elements employ their, reciprocal action and passion to 
generate the compounds : those who derive things from 
a single element are equally compelled to introduce ' acting'.^ 
And in this respect Diogenes is right when he argues that 

15 ' unless all things were derived from one, reciprocal action 
and passion could not have occurred '.^ The hot thing, 
e. g., would not be cooled and the cold thing in turn be 
warmed : for heat and cold do not change reciprocally into 
one another, but what changes (it is clear) is the substrattcm. 
Hence, whenever there is action and passion between two 
things, that which underlies them must be a single some- 
thing. No doubt, it is not true to say that <a:// things are of 

20 this character : ^ but it is true of all things between which 
there is reciprocal action and passion. 

But if we must investigate ' action-passion ' arrd ' com- 
bination ', we must also investigate 'contact'. For action 
and passion (in the proper sense of the terms) can only 
occur between things which are such as to touch one 

25 another; nor can things enter into combination at all un- 
less they have come into a certain kind of contact. Hence 

^ I have added the explicit reference to ' the pluralists' at ^^6 and to 
'the monists' at '^9, because Aristotle's argument in the present 
passage presupposes this classification and the consequences that were 
drawn ffom it in the first chapter. 

^ Cf. Diogenes, fr. 2 (Diels, p. 334). 

•* i.e. are transformations of a single substratum^ or 'derived from 
one thing ' as Diogenes maintained. 



BOOK I. 6 322^ 

we must give a definite account of these three things — of 
* contact ', ' combination ', and ' acting '. 

Let us start as follows. All things which admit of 
'combination' must be capable of reciprocal contact: and 
the same is true of any two things, of which one ' acts' and 
the other ' suffers action ' in the proper sense of the terms. 
For this reason we must treat of ' contact ' first. 

Now every term which possesses a variety of meanings 30 
includes those various meanings either owing to a mere 
coincidence of language, or owing to a real order of deriva- 
tion in the different things to which it is applied: but, 
though this may be taken to hold of 'contact' as of all such 
terms, it is nevertheless true that * contact ' in the proper 
sense applies only to things which have 'position'. And 
' position ' belongs only to those things which also have 
a ' place ' : for in so far as we attribute ' contact ' to the 323^ 
mathematical things, we must also attribute * place' to them, 
whether they exist in separation or in some other fashion.^ 
Assuming, therefore, that ' to touch ' is — as we have defined 
it in a previous work ^ — ' to have the extremes together ', 
only those things will touch one another which, being 5 
separate magnitudes and possessing position, have their 
extremes ' together '. And since position belongs only to 
those things which also have a ' place ', while the primary 
differentiation of ' place ' is ' the above ' and ' the below ' 
(and the similar pairs of opposites), all things which touch 
one another will have ' weight ' or ' lightness ' — either both 
these qualities or one or the other of them.^ But bodies 
which are heavy or light are such as to 'act' and ' suffer 10 
action '. Hence it is clear that those things are by nature 
such as to touch one another, which (being separate magni- 
tudes) have their extremes 'together' and are able to move, 
and be moved by, one another. 

The manner in which the ' mover ' moves the ' moved ' is 

* i.e. whether they exist in separation from the perceptible things, 
or whether they ' are ' e. g. as inseparable adjectives of the (pvaiKct 
o-cb/xara or as abstracted objects of thought. 

^ Cf. F/iyszcs 226^^ 21-2^. 

^ i. e. if A and B are in reciprocal contact, cither A must be heavy 
and B light, or A light and B heavy : or A and B must both be heavy, 
or both be light. 



323^ DE GENERATIONE ET CORRUPTIONE 

not always the same : on the contrary, whereas one kind 
of * mover ' can only impart motion by being itself moved, 
another kind can do so Jhough remaining itself unmoved. 

J5 Clearly therefore we must recognize a corresponding variety 
in speaking of the ' acting ' thing too : for the ' mover ' is said 
to ' act ' (in a sense) and the ' acting ' thing to 'impart motion'. 
Nevertheless there is a difference and we must draw a dis- 
tinction. For not every ' mover ' can * act \ if {a) the term 
'agent' is to be used in contrast to 'patient' and {b) 'patient' 
is to be applied only to those things whose motion is a 'quali- 

20 tative affection ' — i. e. a quality, like ' white ' or ' hot ', in 
respect to which they are ' moved ' only in the sense that 
they are ' altered ' : on the contrary, to ' impart motion ' is 
a wider term than to ' act '.^ Still, so much, at any rate, is 
clear: the things which are 'such as to impart motion', if 
that description be interpreted in one sense, will touch the 
things which are ' such as to be moved by them ' — while 
they will not touch them, if the description be interpreted 
in a different sense. But the disjunctive definition of 
'touching' must include and distinguish (a) 'contact in 
general ' as the relation between two things which, having 
position, are such that one is able to impart motion and the 
other to be moved, and {b) 'reciprocal contact' as the rela- 
tion between two things, one able to impart motion and 
the other able to be moved in such a way that ' action and 

35 passion ' are predicable of them. 

As a rule, no doubt, if A touches B, B touches A. For 
indeed practically all the ' movers ' within our ordinary 
experience impart motion by being moved : in their case, 
what touches inevitably must, and also evidently does, 
touch something which reciprocally touches it. Yet, if A 
moves B, it is possible — as we sometimes express it — for 
A ' merely to touch ' B, and that which touches need not 
touch a something which touches it. Nevertheless it is 
commonly supposed that 'touching' must be reciprocal. 
The reason of this belief is that ' movers ' which belong to 
the same kind as the ' moved ' impart motion by being 
moved. Hence if anything imparts motion without itself 
^ i. e. if to ' act ' be understood in the narrow sense just explained. 



.30 



BOOK I. 6 323^ 

being moved, it may touch the ' moved ' and yet itself be 
touched by nothing — -for we say sometimes that the man 
who grieves us ' touches ' us, but not that we ' touch ' him. 

The account just given may serve to distinguish and 
define the ' contact ' which occurs in the things of Nature. 
7 Next in order we must discuss ' action ' and ' passion \ 323^ 
The traditional theories on the subject are conflicting. For 
(i) most thinkers are unanimous in maintaining [a) that 'like' 
is always unaffected by ' like ', because (as they argue) 
neither of two ' likes ' is more apt than the other either to 5 
act or to suffer action, since all the properties which belong 
to the one belong identically and in the same degree to the 
other ; and (b) that ' unlikes ', i.e. ' differents ', are by nature 
such as to act and suffer action reciprocally. For even 
when the smaller fire is destroyed by the greater, it suffers . 
this effect (they say) owing to its 'contrariety' — since the 
great is contrary to the small. But (ii) Demokritos dis- 10 
sented from all the other thinkers and maintained a theory 
peculiar to himself He asserts that agent and patient are 
identical, i. e. ' like '. It is not possible (he says) that 
'others', i.e. 'differents', should suffer action from one 
another : on the contrary, even if two things, being 'others', 
do act in some way on one another, this happens to them 15 
not qua ' others ' but qt/a possessing an identical property. 

Such, then, are the traditional theories, and it looks as 
if the statements of their advocates were in manifest conflict. 
But the reason of this conflict is that each group is in fact 
stating a part, whereas they ought to have taken a compre- 
hensive view of the subject as a whole. For (i) if A and B 
are ' like ' — absolutely and in all respects without difference 
from one another — it is reasonable to infer that neither is 20 
in any way affected by the other. Why, indeed, should 
either of them tend to act any more than the other? 
Moreover, if ' like ' can be affected by ' like ', a thing can also 
be affected by itself: and yet if that were so — if ' like ' tended 
in fact to act qua Mike' — there would be nothing indestruct- 
ible or immovable, for everything would move itself. And 
(ii) the same consequence follows if A and B are absolutely 25 
' other ', i. e. in no respect identical. Whiteness could not 
be affected in any way by line nor line by whiteness — 



323^ DE GENERATIONE ET CORRUPTIONE 

except perhaps ' coincidentally ', viz. if the line happened 
to be white or black : for unless two things either are, or are 
composed of, * contraries ', neither drives the other out of 

-30 its natural condition. But (iii) since only those things 
u^hich either involve a ' contrariety ' or are * contraries ' — 
and not any things selected at random — are such as to 
suffer action and to act-, agent and patient must be ' like ' 
(i.e. identical) in kind and yet 'unlike' (i.e. contrary) in 
species. (For it is a law of nature that body is affected by 
body, flavour by flavour, colour by colour, and so in 
324 general what belongs to any kind by a member of the same 
kind — the reason being that ' contraries ' are in every case 
within a single identical kind, and it is ' contraries ' which 
reciprocally act and suffer action.) Hence agent and patient 
must be in one sense identical, but in another sense other 
5 than (i.e. 'unlike') one another. And since (a) patient and 
agent are generically identical (i.e. 'like') but specifically 
' unlike ', while (b) it is ' contraries ' that exhibit this charac- 
ter : it is clear that ' contraries ' and their ' intermediates ' 
are such as to suffer action and to act reciprocally — for indeed 
it is these that constitute the entire sphere of passing-away 
and coming-to-be. 

10 We can now understand why fire heats and the cold thing 
cools, and in general why the active thing assimilates to 
itself the patient. For agent and patient are contrary to 
one another, and coming-to-be is a process into the con- 
trary : hence the patient imist change into the agent, since 
it is only thus that coming-to-be will be a process into the 
contrary. And, again, it is intelligible that the advocates 
of both views, although their theories are not the same, are 

15 yet in contact with the nature of the facts. For sometimes 
we speak of the stibstratum as suffering action (e. g. of ' the 
man ' as being healed, being warmed and chilled, and simi- 
larly in all the other cases), but at other times we say ' what is 
cold is being warmed ', ' what is sick is being healed ' : and 
in both these ways of speaking we express the truth, since 
in one sense it is the 'matter', while in another sense it is 
the ' contrary ', which suffers action. (We make the same 

20 distinction in speaking of the agent : for sometimes we say 
that ' the man ', but at other times that ' what is hot ', pro- 



BOOK I. 7 324^ 

duces heat.) Now the one group of thinkers supposed that 
agent and patient must possess something identical, because 
they fastened their attention on the substratum : while the 
other group maintained the opposite because their attention 
was concentrated on the ' contraries '. x 

We must conceive the same account to hold of action 25 
and passion as that which is true of ' being moved ' and 
' imparting motion '. For the ' mover ', like the ' agent ', has 
two meanings. Both (a) that which contains the origina- 
tive source of the motion is thought to ' impart motion ' (for 
the originative source is first amongst the causes), and also 
(d) that which is last, i. e. immediately next to the moved 
thing and to the coming-to-be.-^ A similar distinction holds 
also of the agent : for we speak not only (a) of the doctor, 3° 
but also (d) of the wine, as healing. Now, in motion, there 
is nothing to prevent the first mover being unmoved (indeed, 
as regards some ' first movers ' this is actually necessary) al- 
though the last mover always imparts motion by being itself 
moved : and, in action, there is nothing to prevent the first 
agent being unaffected, while the last agent only acts by 
suffering action itself. For {a) if agent and patient have not 
the same matter, agent acts without being affected : thus 35 
the art of healing produces health without itself being acted 
upon in any way by that which is being healed. But 324^ 
{b) the food, in acting, is itself in some way acted upon : 
for, in acting, it is simultaneously heated or cooled or 
otherwise affected. Now the art of healing corresponds 
to an ' originative source ', while the food corresponds to 
* the last ' (i. e. ' contiguous ') mover.^ 

Those active powers, then, whose forms are not embodied 5 
in matter, are unaffected : but those whose forms are in 
matter are such as to be affected in acting. For we main- 
tain that one and the same ' matter ' is equally, so to say, 
the basis of either of the two opposed things — being as it 
were a ' kind ' ; ^ and that that which can be hot must be 
made hot, provided the heating agent is there, i. e. comes 
near. Hence (as we have said) some of the active powers 10 

^ By ' the coming-to-be ' {ji]v yeVecrti/) we must apparently understand 
'that which is coming-to-be' {to yiuofxevou). 
2 Cf. above, 324^ 26-9. 

^ i. e. a kind, of which the two opposed things are contrasted species. 

D 2, 



324^ DE GENERATIONE ET CORRUPTIONE 

are unaffected while others are such as to be affected ; and 
what holds of motion is true also of the active powers. 
For as in motion ' the first mover ' is unmoved, so among 
the active powers * the first agent ' is unaffected. 

The active power is a ' cause ' in the sense of that from 
which the process originates : but the end, for the sake of 
1 5 which it takes place, is not * active '. (That is why health 
is not 'active', except metaphorically.) For when the 
agent is there, the patient becomes something: but when 
' states ' ^ are there, the patient no longer becomes but 
already is — and 'forms' (i.e. ' ends ') are a kind of * state'. 
As to the ' matter ', it (qua matter) is passive. Now fire con- 
tains 'the hot' embodied in matter: but a 'hot' separate from 
20 matter (if such a thing existed) could not suffer any action. 
Perhaps, indeed, it is impossible that ' the hot ' should exist 
in separation from matter : but if there are any entities thus 
separable, what we are saying would be true of them. 

We have thus explained what action and passion are, 
what things exhibit them, why they do so, and in what 
25 manner. We must go on ^ to discuss how it is possible for 8 
action and passion to take place. 

Some philosophers think that the ' last ' agent — the ' agent ' 
in the strictest sense — enters in through certain pores, and 
so the patient suffers action. It is in this way, they assert, 
that we see and hear and exercise all our other senses. 
Moreover, according to them, things are seen through air 
30 and water and other transparent bodies, because such 
bodies possess pores, invisible indeed owing to their minute- 
ness, but close-set and arranged in rows : and the more 
transparent the body, the more frequent and serial they 
suppose its pores to be. 

Such was the theory which some philosophers (including 

Empedokles) advanced in regard to the structure of certain 

bodies. They do not restrict it to the bodies which act 

and suffer action : but ' combination ' too, they say, takes 

55 place ' only between bodies whose pores are in reciprocal 

symmetry '. The most systematic and consistent theory, 

325^ however, and one that applied to all bodies, was advanced 

^ i.e. like 'health \ 

2 For this sense of iraXiv see Bonitz, Index 559^i3ff- Perhaps, 
however, Aristotle means 'We must go back and discuss'. 



BOOK I. 8 325' 

by Leukippos and Demokritos : and, in maintaining it, they 
took as their starting-point what naturally comes first.^ 

For some of the older philosophers ^ thought that ' what 
is ' must of necessity be ' one ' and immovable. The void, 
they argue, ' is not ' : but unless there is a void with a 5 
separate being of its own, 'what is ' cannot be moved — nor 
again can it be 'many', since there is nothing to keep 
things apart. And in this respect,^ they insist, the view 
that the universe is not ' continuous ' but ' discretes-in-con- 
tact' ^ is no better than the view that there are 'many' (and 
not ' one ') and a void.^ For (suppose that the universe is 
discretes-in-contact. Then),^ if it is divisible through and 
through, there is no ' one ', and therefore no ' many ' either, 
but the Whole is void ; while to maintain that it is divisible 
at some points, but not at others, looks like an arbitrary 10 
fiction. For up to what limit is it divisible? And for 
what reason is part of the Whole indivisible, i.e. 2^ plenum^ 
and part divided ? Further, they maintain, it is equally ''' 
necessary to deny the existence of motion. 

Reasoning in this way, therefore, they were led to tran- 
scend sense-perception, and to disregard it on the ground 
that ' one ought to follow the argument ' : and so they 
assert that the universe is 'one' and immovable. Some of ^5 
them add that it is ' infinite ', since the limit (if it had one) 
would be a limit against the void.*^ 

There were, then, certain thinkers who, for the reasons 
we have stated, enunciated views of this kind as their 
theory of ' The Truth '.^ ... Moreover,^^ although these 

^ Perhaps we should read Kara (pvcriv, ^nep eanv and understand the 
words as a reference to Parmenides (cf. e.g. fr. 8, 1. i; Diels, p. 118}. 

^ The reference is to Parmenides, Melissos, and (probably) Zeno. 

^ i. e. for rendering intelligible the being of a ' many '. 

* This appears to be the view of Empedokles, as Aristotle here 
expresses it : cf. below, 325^ 5-10. 

° This appears to be the view of the Pythagoreans : cf. Physics 
213^22-7. 

® I have added these words to bring out the connexion of thought, 
which is clear enough in the original without any addition. 

'^ i.e. the existence of motion is just as impossible on the hypothesis 
of Empedokles as on that of the Pythagoreans. 

^ Cf. Melissos, e.g. fr. 3, 5, 7 (Diels, pp. 144, 145). 

^ These words (Tr^pi t?)? aKr]6das) seem to be intended to suggest 
' The Way of Truth ' in the poem of Parmenides. 

^° One or more arguments against the Eleatic theory appear to have 
dropped out before en in ^ 17. 



325^ DE GENERATIGNE ET CORRUPTIONE 

opinions appear to follow logically in a dialectical dis- 
cussion, yet to believe them seems next door to madness 

20 when one considers the facts. For indeed no lunatic seems 

. to be so far out of his senses as to suppose that fire and ice 
are ' one ' : it is only between what is right, and what seems 
right from habit, that some people are mad enough to see 
no difference. 

Leukippos, however, thought he had a theory which 
harmonized with sense-perception and would not abolish 

25 either coming-to-be and passing-away or motion and the 
multiplicity of things. He made these concessions to the facts 
of perception: on the other hand, he conceded to the Monists 
that there could be no motion without a void. The result 
is a theory which he states as follows: 'The void is a "not- 
' being ", and no part of " what is " is a " not-being" ; for 
' what " is " in the strict sense of the term is an absolute 
^plenum. This plemim^ however, is not '* one " : on the 

30 ' contrary, it is a "many" infinite in number and invisible 
' owing to the minuteness of their bulk. The " many " 
' move in the void (for there is a void) ^ : and by coming 
' together they produce " coming-to-be ", while by separating 
' they produce " passing-away ".^ Moreover, they act and 
' suffer action wherever they chance to be in contact (for 

* there they are not " one "), and they generate by being put 
' together and becoming intertwined. From the genuinely- 

35 ' one, on the other hand, there never could have come-to-be 

* a multiplicity, nor from the genuinely-many a " one " : 
325'' ' that is impossible. But ' (just as Empedokles and some of 

the other philosophers say that things suffer action through 
their pores,^ ^so) 'all ''alteration" and all "passion" take 
' place in the way that has been explained : breaking-up (i. e. 
' passing-away) is effected by means of the void, and so too 
5 ' is growth — solids creeping in to fill the void places.' 

Empedokles too is practically bound to adopt the same 

^ i. e. there is a void, though it is a ' not-being ' or ' unreal '. 

2 I am greatly indebted to the translation given by Burnet (§ 173) 
of 324^35— 325^32, though I have not been able to accept his version 
in all its details. 

3 The comparison with 'Empedokles and some of the other philo- 
sophers ' is of course not part of the argument which Aristotle is here 
reproducing from Leukippos. 



BOOK I. 8 325^ 

theory as Leukippos. For he must say that there are 
certain solids which, however, are indivisible — unless there 
are continuous pores all through the body. But this last 
alternative is impossible : for then there will be nothing 
solid in the body (nothing beside the pores) but all of it 
will be void. It is necessary, therefore, for his ' contiguous 
discretes ' to be indivisible, while the intervals between 10 
them — which he calls ' pores ' — must be void. But this is 
precisely Leukippos's theory of action and passion. 

Such, approximately, are the current explanations of the 
manner in which some things 'act' while others 'suffer 
action '. And as regards the Atomists, it is not only clear 
what their explanation is : it is also obvious that it follows 
with tolerable consistency from the assumptions they employ. ^5 
But there is less obvious consistency in the explanation 
offered by the other thinkers. It is not clear, for. instance, 
how, on the theory of Empedokles, there is to be ' passing- 
away ' as well as ' alteration '. For the primary bodies of 
the Atomists— the primary constituents of which bodies are 
composed, and the ultimate elements into which they are 
dissolved — are indivisible, differing from one another only in 
figure. In the philosophy of Empedokles, on the other 
hand, it is evident that all the other bodies down to the 20 
' elements ' have their coming-to-be and their passing- 
away : but it is not clear how the ' elements ' themselves, 
severally in their aggregated masses, come-to-be and pass- . 
away. Nor is it possible for Empedokles to explain how 
they do so, since he does not assert that Fire too ^ (and 
similarly every one of his other ' elements ') possesses ' ele- 
mentary constituents ' of itself. 

Such an assertion would commit him to doctrines like 
those which Plato has set forth in the Timaeiis} For 25 
although both Plato and Leukippos postulate elementary 
constituents that are indivisible and distinctively charac- 
terized by figures, there is this great difference between the 
two theories : the ' indivisibles ' of Leukippos (i) are solids, 
while those of Plato are planes, and (ii) are characterized 
by an infinite variety of figures, while the characterizing 

^ i.e. as well as the composite bodies. 
^ Cf, Timaeus 53 off. 



325^ DE GENERATIONE ET CORRUPTIONE 

figures employed by Plato are limited in number. Thus 
30 the ' comings-to-be ' and the ' dissociations ' result from the 
'indivisibles' (a) according to Leiikippos through the void and 
through contact (for it is at the point of contact that each of 
the composite bodies is divisible^), but {b) according to Plato 
in virtue of contact alone, since he denies there is a void. 

Now we have discussed ' indivisible planes ' in the pre- 
ceding treatise.^ But with regard to the assumption of 
35 ' indivisible solids ', although we must not now enter upon 
a detailed study of its consequences, the following criticisms 
fall within the compass of a short digression : — 
326^ (I) The Atomists are committed to the view that every 'in- 
divisible ' is incapable alike of receiving a sensible property 
(for nothing can 'suffer action' except through the void) and 
of producing one — no ' indivisible ' can be. e.g., either hard 
or cold.^ Yet it is surely a paradox that an exception is 
5 made of ' the hot ' — ' the hot ' being assigned as peculiar to 
the spherical figure : for, that being so, its ' contrary ' also 
(' the cold') is bound to belong to another of the figures.. 
If, however, these properties (heat and cold) do belong to 
the ' indivisibles ', it is a further paradox that they should 
not possess heaviness and lightness, and hardness and 
10 softness. And yet Demokritos says 'the more any in- 
divisible exceeds, the heavier it is' — to which we must 
clearly add ' and the hotter it is '. But if that is their 
character, it is impossible they should not be affected 
by one another: the 'slightly-hot indivisible', e.g., will 
inevitably suffer action from one which far exceeds it in 
heat.* Again, if any ' indivisible ' is ' hard ', there must 
also be one which is ' soft ' : but ' the soft ' derives its very 
name from the fact that it suffers a certain action — for 
' soft ' is that which yields to pressure. (II) But further, 

* Cf. above, 325*^32-4. 

^ Cf. de Caelo Y. i, especially 298^^33fTf., r. 7 and A. 2. 

' Or perhaps this clause is a quotation: 'since "no indivisible can 
be either hard or cold".' 

^ If, as Demokritos asserts, the 'indivisibles' differ in weight, being 
heavy in direct proportion to their mass, his ' spherical indivisibles ' 
(Aristotle argues) must differ in the degree of their heat on the same 
principle. But if A is hotter than B, 15 is susceptible to the action of 
A. Hence Demokritos has violated a fundamental thesis of his own 
theory (cf. 326*^ 1-2), viz. that every 'indivisible' must be dnades. 



BOOK I. 8 326^ 

not only is it paradoxical (i) that no property except figure 15 
should belong to the ' indivisibles ' : it is also paradoxical 
(ii) that, if other properties do belong to them, one only of 
these additional properties should attach to each — e.g. that 
this ' indivisible ' should be cold and that ' indivisible ' hot. 
For, on that supposition, their substance would not even be 
uniform.^ And it is equally impossible (iii) that more than 
one of these additional properties should belong to the 
single ' indivisible '. For, being indivisible^ it will possess 
these properties in the same point ^ — so that, if it ' suffers 
action ' by being chilled^ it will also, qua chilled, ' act * or 20 
' suffer action ' in some other way. And the same line of 
argument applies to all the other properties too : for the 
difficulty we have just raised confronts, as a necessary con- 
sequence, all who advocate ' indivisibles ' (whether solids or 
planes), since their ' indivisibles ' cannot become either 
'rarer' or 'denser' inasmuch as there is no void in them. 
(Ill) It is a further paradox that there should be small 25 
' indivisibles ', but not large ones. For it is natural enough, 
from the ordinary point of view, that the larger bodies 
should be more liable to fracture than the small ones, since 
they (viz. the large bodies) are easily broken up because 
they collide with many other bodies. But why should 
indivisibility as such be the property of small, rather than 
of. large, bodies? (IV) Again, is the substance of all those 30 
solids uniform, or do they fall into sets which differ from 
one another — as if, e. g., some of them, in their aggregated 
bulk,^ were ' fiery ', others ' earthy ' ? For (i) if all of them 
are uniform in substance, what is it that separated one from 
another ? Or why, when they corne into contact, do they 
not coalesce into one, as drops of water run together when 
drop touches drop (for the two cases are precisely parallel)? 
On the other hand (ii) if they fall into differing sets, how 
are these characterized ? It is clear, too, that these!" rather 35 
than the ' figures ', ought to be postulated as ' original reals ', 326^ 

^ The uniformity of the substance or ' stuff' of the atoms was 
a fundamental doctrine in the theory. Cf. Physics 203=* 34 - ^ 2, 
de Caelo 275^31-2; Burnet, p. 3363. 

^ i. e. in its single, indivisible, undifferentiated identity. 

^ Cf. above, 325^22. 

^ i.e. these qualitatively-distinct sets of atoms. 



326^ DE GENERATIONE ET CORRUPTIONE 

i.e. causes from which the phenomena result. Moreover, 
if they differed in substance, they would both act and suffer 
action on coming into reciprocal contact. (V) Again, 
what is it which sets them moving ? For if their ' mover ' 
is other than themselves, they are such as to ' suffer action '. 
If, on the other hand, each of them sets itself in motion, 
either (a) it will be divisible (' imparting motion ' qua this, 
5 ' being moved ' qua that), or {b) contrary properties will 
attach to it in the same respect — i. e. ' matter ' will be 
identical-in-potentiality as well as numerically-identical.^ 

As to the thinkers who explain modification of property 
through the movement facilitated by the pores, if this is 
supposed to occur notwithstanding the fact that the pores 
are filled, their postulate of pores is superfluous.' For if the 
whole body suffers action under these conditions, it would 

lo suffer action in the same way even if it had no pores but 
were just its own continuous self. Moreover, how can their 
account of ' vision through a medium ' be correct ? It is 
impossible for (the visual ray)^ to penetrate the transparent 
bodies at their ' contacts ' ; and impossible for it to pass 
through their pores if every pore be full. For how will that ^ 
differ from having no pores at all ? The body will be 

15 uniformly ' full ' throughout. But, further, even if these 
passages, though they must contain bodies, are ' void ', the 
same consequence will follow once more.* And if they are 
'too minute to admit any body', it is absurd to suppose 
there is a ' minute ' void and yet to deny the existence of 
a ' big ' one (no matter how small the 'big ' may be ^), or to 
imagine ' the void ' means anything else than a body's place 

20 — whence it clearly follows that to every body there will 
correspond a void of equal cubic capacity. 

^ For the docirine implied in this argument, cf Physics 190'' 24, 
192*1 ff. 

^ I have added these words because Aristotle is referring to 
Empedokles's theory of vision. Cf. Empedokles, fr. 84 (Diels, 
pp. 196-7) ; Plato, li77iaeiis 45 Bff. 

^ sc. having pores, all of which are ' full '. 

* i.e. the body will still be impenetrable, even if the pores as such 
(as channels) are distinguished in thought from what fills them. For 
in fact the pores are always 'full' and the body is a plemim through- 
out- ihougli perhaps not a '' wmionw'' pie fiuni. 

■' 'I5ig' is a relative term and may include a void in any degree 
bigger than the infinitesimal. 



BOOK I. 8 326^ 

As a general criticism we must urge that to postulate 
pores is superfluous. For if the agent produces no effect 
by touching the patient, neither will it produce any by 
passing through its pores. On the other hand, if it acts 
by contact, then — even without pores — some things will 
' suffer action ' and others will ' act ', provided they are by 
nature adapted for reciprocal action and passion. Our 
arguments have shown that it is either false or futile to 25 
advocate pores in the sense in which some thinkers conceive 
them. But since bodies are divisible through and through, 
the postulate of pores is ridiculous : for, qua divisible, a body 
can fall into separate parts.^ 

9 Let us explain the way in which things in fact possess 
the power of generating, and of acting and suffering action : 30 
and let us start from the principle we have often enunciated. 
For, assuming the distinction between {a) that which is 
potentially and {b) that which is actually such-and-such, it 
is the nature of the first, precisely in so far as it is what it 
is, to suffer action through and through, not merely to be 
susceptible in some parts while insusceptible in others. But 
its susceptibility varies in degree, according as it is more 
or less such-and-such, and one would be more justified in 
speaking of ' pores ' in this connexion ^ : for instance, in the 
metals there are veins of ' the susceptible ' stretching con- 35 
tinuously through the substance. 327^ 

So long, indeed, as any body is naturally coherent and 
one, it is insusceptible. So, too, bodies are insusceptible so 
long as they are not in contact either with one another or 
with other bodies which are by nature such as to act and 
suffer action. (To illustrate my meaning : Fire heats not 
only when in contact, but also from a distance. For the 
fire heats the air, and the air — being by nature such as both 5 
to act and suffer action — heats the body.) But the supposi- 
tion that a body is ' susceptible in some parts, but insus- 
ceptible in others' (is only possible for those who hold an 
erroneous view concerning the divisibility of magnitudes. 

^ Cf. above, 316^28-9. Division eo ipso opens a channel in the 
body. 

^ viz. to express such lines of greater susceptibility. 



327^ DE GENERATIONE ET CORRUPTIONE 

For usy the following account results from the distinctions 
we established at the beginning.^ For (i) if magnitudes are 
not divisible through and through — if, on the contrary, 
there are indivisible solids or planes — then indeed no body 
would be susceptible through and through : but neither 

ro would any be continuous. Since, however, (ii) this is false, 
i. e. since every body is divisible, there is no difference be- 
tween ' having been divided into parts which remain in 
contact ' and ' being divisible \ For if a body ' ccm be 
separated at the contacts' (as some thinkers express it), 
then, even though it has not yet been divided, it will be in 
a state of dividedness — since, as it ca7i be divided, nothing 
inconceivable results/'^ And (iii) the supposition is open to. 

15 this general objection — it is a paradox that ' passion ' should 
occur in this manner only, viz. by the bodies being split. 
For this theory abolishes ' alteration ' : but we see the same 
body liqtiid at one time and solid at another, without losing 
its continuity. It has suffered this change not by 'division' 
and ' composition '; nor yet by ' turning ' and ' intercontact ' 

20 as Demokritos asserts ; for it has passed from the liquid to 
the solid state without any change of ' grouping ' or 
* position ' in the constituents of its substance.* Nor are 
there contained within it those ' hard ' (i. e. congealed) 
particles ' indivisible in their bulk ' : on the contrary, it is 
liquid — and again, solid and congealed — uniformly all 
through. This theory, it must be added, makes growth 
and diminution impossible also. For if there is to be 
apposition (instead of the growing thing having changed as 

25 a whole, either by the admixture of something or by its 
own transformation), increase of size will not have resulted 
in any and every part.'' 

So much, then, to establish that things generate and are 
generated, act and suffer action, reciprocally ; and to dis- 
tinguish the way in which these processes can occur from 
the (impossible) way in which some thinkers say they occur. 

^ A clause to this effect appears to have dropped out before hwp'i- 
(TdUTas- in '^6. 

"^ Cf. above, 316"' 14— 317* 17. 

■'' i.e. if this potentiality be realized: cf. 316*19. The argument 
turns on Aristotle's conception of ro dvparov: cf. Metaph. 1047=^24-6. 

^ Cf. above, 315^33— 316"' I. ^ Cf. above, 321*2-26. 



BOOK I. lo 327^ 

10 But we have still to explain ' combination ', for that was the 30 
third of the subjects we originally^ proposed to discuss. 
Our explanation will proceed on the same method as before. 
We must inquire : What is ' combination ', and what is that 
which can 'combine'? Of what things, and under what 
conditions, is ' combination ' a property ? And, further, 
does ' combination ' exist in fact, or is it false to assert its 
existence ? 

For, according to some thinkers, it is impossible for one 35 
thing to be combined with another. They argue that (i) if 
both the ' combined ' constituents persist unaltered, they are 327^ 
no more ' combined ' now than they were before, but are in 
the same condition : while (ii) if 07ie has been destroyed, 
the constituents have not been ' combined ' — on the contrary, 
one constituent is and the other is not, whereas 'com- 
bination ' demands uniformity of condition in them both : 
and on the same principle (iii) even if both the combining 5 
constituents have been destroyed as the result of their 
coalescence, they cannot ' have been combined ' since they 
have no being at all. 

What we have in this argument is, it would seem, 
a demand for the precise distinction of ' combination ' from 
coming-to-be and passing-away (for it is obvious that ' com- 
bination \ if it exists, must differ from these processes) and 
for the precise distinction of the ' combinable ' from that 
which is such as to come-to-be and pass-away. As soon, 
therefore, as these distinctions are clear, the difficulties 10 
raised by the argument would be solved. 

Now (i) we do not speak of the wood as * combined ' with 
the firCj nor of its burning as a ' combining ' either of its 
particles with one another or of itself with the fire : what 
we say is that 'the fire is coming-to-be, but the wood is 
passing-away '. Similarly, we speak neither (ii) of the food 
as ' combining ' with the body, nor (iii) of the shape as ' com- 15 
bining' with the wax and thus fashioning the lump. Nor 
can body ' combine ' with white, nor (to generalize) ' pro- 
perties ' and ' states ' with * things ' : for we see them persist- 
ing unaltered.^ But again (iv) white and knowledge cannot 

' Cf. above, 322^ 5 ff. 

2 sc. in the resulting^complex (e.g. 'white-body' or Mearned-man '}. 



327"' DE GENERATIONE ET CORRUPTIONE 

be ' combined ' either, nor any other of the ' adjectivals '. 

20 (Indeed, this is a blemish in the theory of those ^ who assert 
that ' once upon a time all things were together and com- 
bined '. For not everything can •' combine ' with everything. 
On the contrary, both of the constituents that are combined 
in the compound must originally have existed in separation : 
but no property can have separate existence.) 

Since, however, some things are-poteiitially while others 
are-actually , the constituents combined in a compound can 
'be' in a sense and yet 'not-be'. The compound may 

35 be-acUially other than the constituents from which it has 
resulted ; nevertheless each of them may still be-potentially 
what it was before they were combined, and both of them 
may survive undestroyed. (For this was the difficulty that 
emerged in the previous argument : and it is evident that the 
combining constituents not only coalesce, having formerly 
existed in separation, but also can again be separated 
out from the compound.) The constituents, therefore, 

30 neither {a\persist actually, as ' body ' and ' white ' persist : 
nor {h) are they destroyed (either one of them or both), for 
their ' power of action ' ^ is preserved. Hence these diffi- 
culties may be dismissed : but the problem immediately 
connected with them — ' whether combination is something 
relative to perception ' — must be set out and discussed. 

When the combining constituents have been divided into 
parts so small, and have been juxtaposed in such a manner, 

35 that perception fails to discriminate them one from another, 
328^ have they then ' been combined ' ? Or ought we to say 
' No, not until any and every part of one constituent is 
juxtaposed to a part of the other'? ^ The term, no doubt, 
is applied in the former sense : we speak, e. g., of wheat 
having been ' combined ' with barley when each grain of 
the one is juxtaposed to a grain of the other. But every 
body is divisible and therefore, since body 'combined'^ 

^ Aristotle is perhaps thinking of the ' Sphere ' of Empedokles, as 
well as of the /uly/Lta of Anaxagoras. 

2 Cf. below, 328^28-31 and 334'^ 8-30. 

^ The difference between these two views — both of which Aristotle 
rejects — is one of degree. According to the first view, the constituents 
are divided into parts too small for the normal vision to discriminate, 
and then shuffled. According to the second, the constituents are 
divided into * least ' parts, i. e. into atoms : and these are shuffled. 

* F'or fuKTov = nLxPh cf. e.g. below, 334^31. 



BOOK I. lo 328^ 

with body is uniform in texture throughout, any and every 
part of each constituent ought to be juxtaposed to a part of 5 
the other. 

No body, however, can be divided into its ' least ' parts : 
and ' composition ' is not identical with ' combination ', but 
other than it. From these premises it clearly follows (i) 
that so long as the constituents are preserved in small par- 
ticles, we must not speak of them as ' combined '. (For this 
will be a ' composition ' instead of a * blending ' or ' com- 
bination ' : nor will every portion of the resultant exhibit 
the same ratio between its constituents as the whole. But 10 
we maintain that, if 'combination' has taken place, the 
compound must be uniform in texture throughout — any 
part of such a compound being the same as the whole, just 
as any part of water is water : whereas, if ' combination ' is 
' composition of the small particles ', nothing of the kind 
will happen. On the contrary, the constituents will only be 
' combined ' relatively to perception : and the same thing 
will be ' combined ' to one percipient, if his sight is not 
sharp, (but not to another,)^ while to the eye of Lynkeus 15 
nothing will be ' combined '.) It clearly follows (ii) that we 
must not speak of the constituents as * combined ' in virtue 
of a division such that any and every part of each is juxta- 
posed to a part of the other : for it is impossible for them 
to be thus divided. Either, then, there is no ' combination ', 
or we have still to explain the manner in which it can take 
place. 

Now, as we maintain,^ some things are such as to act 
and others such as to suffer action from them. Moreover, 
some things — viz. those which have the same matter — 20 
' reciprocate ', 1. e. are such as to act upon one another and 
to suffer action from one another ; while other things, viz. 
agents which have not the same matter as their patients, 
act without themselves suffering action. Such agents cannot 
* combine ' — that is why neither the art of healing nor health 
produces health by 'combining' with the bodies of the 
patients. Amongst those things, however, which are reci- 

^ The words I have added represent the antithesis implied by the 
beginning of the sentence : but Aristotle prefers to clinch his argument 
by the reference to Lynkeus, at the cost of a slight anacoluthon. 

2 Cf. above, I. 7. 



328^ DE GENERATIONE ET CORRUPTIONE 

procally active and passive, some^re easily-divisible. Now 
(i) if a great quantity (or a large bulk) of one of these easily- 

25 divisible ' reciprocating ' materials be brought together with 
a little (or with a small piece) of another, the effect produced 
is not ' combination ', but increase of the dominant : for the 
other material is transformed into the dominant. (That is 
why a drop of wine does not 'combine' with ten thousand 
gallons of water : for its form is dissolved, and it ^ is changed 
so as to merge in the total volume of water.) On the other 
hand (ii) when there is a certain equilibrium between their 

30 ' powers of action ', then each of them changes out of its own 
nature towards the dominant : yet neither becomes the other, 
but both become an intermediate with properties common 
to both.2 

Thus it is clear that only those agents are * combinable ' 
which involve a contrariety — for these are such as to suffer 
action reciprocally. And, further, they combine more 
freely if small pieces of each of them are juxtaposed. 
For in that condition they change one another more easily 

35 and more quickly ; whereas this effect takes a long time 
when agent and patient are present in bulk. 
328^ Hence, amongst the divisible susceptible materials, those 
whose shape is readily adaptable have a tendency to com- 
bine : for they are easily divided into small particles, since 
that is precisely what ' being readily adaptable in shape ' 
implies. For instance, liquids are the most * combinable ' 
of all bodies — because, of all divisible materials, the liquid 
is most readily adaptable in shape, unless it be viscous. 

5 Viscous liquids, it is true, produce no effect except to 
increase the volume and bulk. But when one of the con- 
stituents is alone susceptible — or superlatively susceptible, 
the other being susceptible in a very slight degree — the 
compound resulting from their combination is either no 
greater in volume or only a little greater. This is what 
happens when tin is combined with bronze. For some 
things display a hesitating and ambiguous attitude towards 

^ sc. the drop of wine. 

^ Each of the constituents, qua acting on the other, is relatively 
'dominant*. Neither of them is absolutely 'dominant', for each 
'suffers action' from the other. Hence each meets the other half- 
way, and the resultant is a compromise between them. 



BOOK I. lo 328^ 

one another — showing a slight tendency to combine and to 
also an inclination to behave as ' receptive matter ' and 
' form ' respectively. The behaviour of these metals is 
a case in point. For the tin almost vanishes, behaving 
as if it were an immaterial property of the bronze : having 
been combined, it disappears, leaving no trace except the 
colour it has imparted to the bronze. The same phenomenon 
occurs in other instances too. 

It is clear, then, from the foregoing account, that 'com- 15 
bination' occurs, what it is, to what it is due, and what 
kind of thing is ' combinable'. The phenomenon depends 
upon the fact that some things are such as to be (a) reci- 
procally susceptible and (^) readily adaptable in shape, 
i. e. easily divisible. For such things can be ' combined ' 
without its being necessary either that they should have 
been destroyed or that they should survive absolutely un- 
altered : and their ' combination ' need not be a * composition', 
nor merely ' relative to perception '. On the contrary : any- 20 
thing is ' combinable ' which, being readily adaptable in 
shape, is such as to suffer action and to act ; and it is 
' combinable with ' another thing similarly characterized 
(for the ' combinable ' is relative to the * combinable ') ; and 
* combination ' is unification of the ' combinables ', resulting 
from their ' alteration ' 



BOOK II 

I We have explained under what conditions ' combination ', 
' contact ', and * action-passion ' are attributable to the things 
which undergo natural change. Further, we have discussed 
* unqualified ' coming-to-be and passing-away, and explained 
under what conditions they are predicable, of what subject, 
and owing to what cause. Similarly, we have also discussed 30 
'alteration', and explained what 'altering' is and how it 



328^ DE GENERATIONE ET CORRUPTIONE 

differs from coming-to-be and passing-away. But we have 
still to investigate the so-called 'elements' of bodies. 

For the complex substances whose formation and main- 
, tenance are due to natural processes all presuppose the 
perceptible bodies as the condition of their coming-to-be 
and passing-away : but philosophers disagree in regard to 
the matter which underlies these perceptible bodies. Some 
maintain it is single, supposing it to be, e. g.. Air or Fire, 

35 or an ' intermediate ' between these two (but still a body 
329^ with a separate existence). Others, on the contrary, postu- 
late two or more materials — ascribing to their ' association ' 
and ' dissociation ', or to their ' alteration ', the coming-to-be 
and passing-away of things. (Some, for instance, postulate 
Fire and Earth : some add Air, making three : and some, 
like Empedokles, reckon Water as well, thus postulating 
four.) 
5 Now we may agree that the primary materials, whose 
change (whether it be * association and dissociation ' or 
a process of another kind) results in coming-to-be and 
passing-away, are rightly described as * originative sources, 
i. e. elements '. But (i) those thinkers are in error who 
postulate, beside the bodies we have mentioned, a single 

10 matter — and that a corporeal and separable matter. For 
this ' body ' of theirs cannot possibly exist without a 
'perceptible contrariety': this 'Boundless', which some 
thinkers identify with the ' original real ', must be either 
light or heavy, either cold or hot.^ And (ii) what Plato 
has written in the Timaeus is not based on any precisely- 
articulated conception. For he has not stated clearly 

15 whether his ' Omnirecipient ' ^ exists in separation from 
the ' elements ' ; nor does he make any use of it. He 
says, indeed, that it is a substratum prior to the so-called 
' elements ' — underlying them, as gold underlies the things 
that are fashioned of gold. (And yet this comparison, 
if thus expressed, is itself open to criticism. Things 

20 which come-to-be and pass-away cannot be called by 
the name of the material out of which they have come- 
to-be : it is only the results of ' alteration ' which retain 
the name of the substratum whose ' alterations ' they 
' Cf. below, 332^20-6. 2 (3f^ Timaeus Si\ 2i. 



BOOK II. I 329^ 

are. However, he actually says ^ that ' far the truest 
account is to affirm that each of them ^ is " gold " '.) Never- 
theless he carries his analysis of the 'elements' — solids 
though they are — back to 'planes',^ and. it is impossible 
for ' the Nurse ' ^ (i. e. the primary matter) to be identical 
with ' the planes '. 

Our own doctrine is that although there is a matter of 
the perceptible bodies (a matter out of which the so-called 25 
* elements ' come-to-be), it has no separate existence, but 
is always bound up with a contrariety. A more precise 
account of these presuppositions has been given in another 
work ^ : we must, however, give a detailed explanation of 
the primary bodies as well, since they too are similarly 
derived from the matter.^ We must reckon as an ' origina- 30 
tive source' and as 'primary' the matter which underlies, 
though it is inseparable from, the contrary qualities : for 
' the hot ' is not matter for ' the cold ' nor ' the cold ' for ' the 
hot ', but the stibstrattnn is matter for them both. We there- 
fore have to recognize three ' originative sources ' : firstly 
that which is potentially perceptible body, secondly the con- 
trarieties (I mean, e. g., heat and cold), and thirdly Fire, 35 • 
Water, and the like. Only ' thirdly ', however : for these 
bodies change into one another (they are not immutable 329 
as Empedokles and other thinkers assert, since ' alteration ' 
would then have been impossible), whereas the contrarieties 
do not change: 

Nevertheless, even so "^ the question remains : What sorts 
of contrarieties, and how many of them, are to be accounted 
' originative sources ' of body ? For all the other thinkers 
assume and use them without explaining why they are 5 
these or why they are just so many. 

2 Since, then, we are looking for 'originative sources' of 

^ Cf. Thnaeus 49 d-50 c. 

^ i. e. each of the things that are ' fashioned of gold '. 

^ Cf. Ti77taeus 53cff. * Cf. Thnaeus, e.g. 49a, 52 d_. 

^ Cf. Physics A. 6-9, where rrpaTr] vXrj and ' the contrariety ' (elSos 
and areprjcris) are accurately defined and distinguished as presupposi- 
tions of yevecris. 

^ The account in the Physics applied generally to the 7eVfcrt9 of any 
and every perceptible body. Aristotle now proposes to apply it to the 
y€V€(TLs of the prifTtary perceptible bodies in particular. 

^ i. e. notwithstanding the sketch Aristotle has just given. 

E 2> 



329^ DE GENERATIONE ET CORRUPTIONE 

perceptible body ; and since ' perceptible ' is equivalent ^ 
to ' tangible ', and ' tangible ' is that of which the perception 
is touch ; it is clear that not all the contrarieties constitute 

10 'forms 'and 'originative sources' of body,but only those which 
correspond to touch. For it is in accordance with a con- 
trariety — a contrariety, moreover, oi tangible qualities — that 
the primary bodies are differentiated. That is why neither 
whiteness (and blackness), nor sweetness (and bitterness), 
nor (similarly) any quality belonging to the other ^ per- 
ceptible contrarieties either, constitutes an ' element '. And 
yet vision is prior to touch, so that its object also is prior 

15 to the object of touch. The object of vision, however, is 
a quality of tangible body not qua tangible, but qua some- 
thing else — qiia something which may well be naturally 
prior to the object of touch. 

-Accordingly, we must segregate the tangible differences 
and contrarieties, and distinguish which amongst them are 
primary. Contrarieties correlative to touch are the following : 

20 hot-cold, dry-moist, heavy-light, hard-soft, viscous-brittle, 
rough-smooth, coarse-fine. Of these (i) heavy and light 
are neither active nor susceptible. Things are not called 
' heavy' and ' light' because they act upon, or suffer action 
from, other things. But the ' elements ' must be reciprocally 
active and susceptible, since they 'combine' and are trans- 
formed into one another. On the other hand (ii) hot and 

25 cold, and dry and moist, are terms, of which the first pair 
implies pozver to act and the second pair susceptibility. 
' Hot ' is that which ' associates ' things of the same kind 
(for ' dissociating ', which people attribute to Fire as its 
function, is ' associating ' things of the same class, since 
its effect is to ehminate what is foreign), while ' cold ' is 

30 that which brings together, i. e. ' associates ', homogeneous 
and heterogeneous things alike. And ' moist ' is that which, 
being readily adaptable in shape, is not determinable by 
any limit of its own: while 'dry' is that which is readily 
determinable by its own limit, but not readily adaptable in 
shape. 

' sc. in this connexion : the tangible qualities are the only qualities 
which characterize all perceptible bodies. 

'^ sc. the other 7ion-tangible perceptible contrarieties. 



BOOK II. 2 329' 

From moist and dry are derived (iii) the fine and coarse, 
viscous and brittle, hard and soft, and the remaining tangible 
differences. For (a) since the moist has no determinate 35 
shape, but is readily adaptable and follows the outline of 
that which is in contact with it, it is characteristic of it 330' 
to be ' such as to fill up '. Now ' the fine ' is ' such as to fill 
up '. For ' the fine ' consists of subtle particles ; but that 
which consists of small particles is ' such as to fill up ', 
inasmuch as it is in contact^ whole with whole — and 'the 
fine ' exhibits this character ^ in a superlative degree. Hence 
it is evident that the fine derives from the moist, while the 
coarse derives from the dry. Again (b) ' the viscous ' derives 5 
from the moist : for ' the viscous ' (e. g. oil) is a ' moist ' modi- 
fied in a certain way. 'The brittle', on the other hand, 
derives from the dry : for ' brittle ' is that which is completely 
dry — so completely, that its solidification has actually been 
due to failure of moisture. Further {c) ' the soft ' derives 
from the moist. For ' soft ' is that which yields to pressure 
by retiring into itself, though it does not yield by total dis- 
placement as the moist does — which explains why the moist 10 
is not ' soft ', although ' the soft ' derives from the moist. 
' The hard ', on the other hand, derives from the dry : for 
'hard' is that which is solidified, and the solidified is dry. 

The terms ' dry ' and ' moist ' have more senses than one. 
For ' the damp ', as well as the moist, is opposed to the dry: 
and again ' the solidified ', as well as the dry, is opposed to 
the moist. But all these qualities derive from the dry and 15 
moist we mentioned first.^ For (i) the dry is opposed to 
the damp : i. e. ' damp ' is that which has foreign moisture 
on its surface (' sodden ' being that which is penetrated to 
its core*), while 'dry'^ is that which has lost' foreign 
moisture. Hence it is evident that the damp will derive 
from the moist, and ' the dry ' which is opposed to it will 
derive from the primary dry. Again (ii) the ' moist ' and the 20 
solidified derive in the same way from the primary pair. 

^ ' in contact ' with the vessel which contains it. 
^ The fine, owing to the subtlety (= the smallness) of its particles, 
leaves no corner of its containing receptacle unfilled. 
^ Cf. above, 329^30-2. 
* sc. by foreign moisture : cf. below, ^ 22. 
^ i. e. the ' dry' which is contrasted with the damp : the ' dried '. 



330^ DE GENERATJONE ET CORRUPTIONE 

For ' moist ' ^ is that which contains moisture of its own 
deep within it ('sodden* being that which is deeply- 
penetrated hy foreign moisture), whereas 'solidified' is that 
which has lost this inner moisture. Hence these too 
derive from the primary pair, the ' solidified ' from the dry 
and the ' liquefiable ' from the moist. 
25 It is clear, then, that all the other differences reduce to 
the first four, but that these admit of no further reduction. 
For the hot is not essentially moist or dry, nor the moist 
essentially hot or cold : nor are the cold and the dry deriva- 
tive forms, either of one another or of the hot and the 
moist. Hence these must be four. 

30 The elementary qualities are four, and any four terms 3 
can be combined in six couples. Contraries, however, refuse 
to be coupled : for it is impossible for the same thing to 
be hot and cold, or moist and dry. Hence it is evident that 
the ' couplings ' of the elementary qualities will be four : 
330 hot with dry and moist with hot, and again cold with dry 
and cold with moist. And these four couples have attached 
themselves to the apparently * simple ' bodies (Fire, Air, 
Water, and Earth) in a manner consonant with theory. 
For Fire is hot and dry, whereas Air is hot and moist 
5 (Air being a sort of aqueous vapour) ; and Water is 
cold and moist, while Earth is cold and dry. Thus the 
differences are reasonably distributed among the primary- 
bodies, and the number of the latter is consonant with 
theory. For all who make the simple bodies ' elements ' 
postulate either one, or two, or three, or four. Now (i) those 

TO who assert there is one only, and then generate everything 
else by condensation and rarefaction, are in effect making 
their ' originative sources ' two, viz. the rare and the dense, 
or rather the hot and the cold : for it is these which are the 
moulding forces, while the 'one'^ underlies them as a 
'matter'. But (ii) those who postulate two from the 
start — as Parmenidcs postulated Fire and Earth — make 

15 the intermediates (e. g. Air and Water) blends of these. 

' i. e. the ' moist ' which is contrasted with the solidified : the 
'liquefiable '. 

^ i. e. the single ' element ' which these monistic theories postulate. 



BOOK II. 3 330 

The same course is followed (iii) by those who advocate 
three} (We may compare, what Plato does in 'The 
Divisions ' : for he makes ' the middle ' a blend.^) Indeed, 
there is practically no difference between those who postu- 
late two and those who postulate //^r^^, except that the former 
split the middle ' element ' into two. while the latter treat it 
as only one. But (iv) some advocate four from the start, 20 
e. g. Empedokles : yet he too draws them together so as to 
reduce them to the two, for he opposes all the others to 
Fire. 

In fact, however, fire and air, and each of the bodies we 
have mentioned, are not simple, but blended. The * simple ' 
bodies are indeed similar in nature to them, but not 
identical with them. Thus the 'simple' body corresponding 
to fire is ' such-as-fire ', not fire : that which corresponds to 
air is ' such-as-air ' : and so on with the rest of them. But 25 
fire is an excess of heat, just as ice is an excess of cold. 
For freezing and boiling are excesses of heat and cold 
respectively. Assuming, therefore, that ice is a freezing of 
moist and cold, fire analogously will be a boiling of dry and 
hot : a fact, by the way, which explains why nothing 
comes-to-be either out of ice or out of fire. 3° 

The 'simple' bodies, since they are four, fall into two 
pairs which belong to the two regions, each to each : for 
Fire and Air are forms of the body moving towards the 
'limit', while Earth and Water are forms of the body which 
moves towards the 'centre'.^ Fire and Earth, moreover, 
are extremes and purest : Water and Air, on the contrary, 331^ 
are intermediates and more like blends. And, further, the 
members of either pair are contrary to those of the other, 
Water being contrary to Fire and Earth to Air; for the 
qualities constituting Water and Earth are contrary to 
those that constitute^ Fire and Air. Nevertheless, since 
they are four, each of them is characterized par excellence 

^ Cf. above, 329^2. Philoponos attributes this trialistic theory to 
Ion of Chios. 

"^ I take 'The Divisions' to mean that section of the Ti7naeiis 
(35 aff.) in which Plato describes the making of the Soul. Aristotle's . 
point is merely that Plato makes 'the middle' of his three kinds of 
' substance ' a ' blend' of the other two. 

^ Cf. de Caelo, e. g. 269^20-9, 308^' 14-33, 3ii* I5 ff- 



331^ DE GENERATIONE ET CORRUPTIONE 

by a single quality: Earth by dry rather than by cold, 
5 Water by cold rather than by moist, Air by moist rather 
than by hot, and Fire by hot rather than by dry. 

It has been estabHshed before^ that the coming-to-be of 4 
the 'simple' bodies is reciprocal. At the same time, it is 
manifest, even on the evidence of perception, that they do 
come- to-be : for otherwise there would not have been 'altera- 

10 tion ', since ' alteration ' is change in respect to the qualities 
of the objects of touch. Consequently, we must explain 
(i) what is the manner of their reciprocal transformation, 
and (ii) whether every one of them can come-to-be out of 
every one — or whether some can do so, but not others. 

Now it is evident that all of them are by nature such as 
to change into one another : for coming-to-be is a change 

>5 into contraries and out of contraries, and the ' elements' all 
involve a contrariety in their mutual relations because their 
distinctive qualities are contrary. For in some of them 
both qualities are contrary — e.g. in Fire and Water, the first 
of these being dry and hot, and the second moist and cold : 
while in others one of the qualities (though only one) is 
contrary — e.g. in Air and Water, the first being moist and 

20 hot, and the second moist and cold. It is evident, therefore, 
if we consider them in general, that every one is by nature 
such as to come-to-be out of every one : and when we come 
to consider them severally, it is not difficult to see the 
manner in which their transformation is effected. For, 
though all will result from all, both the speed and the 
facility of their conversion will differ in degree. 

25 Thus (i) the process of conversion will be quick between 
those which have interchangeable ' complementary factors ', 
but slow between those which have none. The reason is 
that it is easier for a single thing to change than for many. 
Air, e.g., will result from Fire if a single quality changes : 
for Fire, as we saw, is hot and dry while Air is hot and 
moist, so that there will be Air if the dry be overcome by 

30 the moist. Again, Water will result from Air if the hot be 
overcome by the cold : for Air, as we saw, is hot and moist 

' The reference is probably neither to 314'' 15-26 nor to 329*^35, but 
to de Caelo 304^^ 23 ff. 



BOOK 11. 4 331^ 

while Water is cold and moist, so that, if the hot changes, 
there will be Water. So too, in the same manner. Earth 
will result from Water and Fire from Earth, since the two 
'elements' in both these couples have interchangeable 
'complementary factors'. For Water is moist and cold 
while Earth is cold and dry — so that, if the moist be over- 35 
come, there will be Earth : and again, since Fire is dry and 
hot while Earth is cold and dry, Fire will result from Earth 331 
if the cold pass-away. 

It is evident, therefore, that the coming-to-be of the 
'simple' bodies will be cyclical; and that this cyclical 
method of transformation* is the easiest, because the co7i- 
secutive ' elements ' contain interchangeable 'complementary 
factors'.^ On the other hand (ii) the transformation of 
Fire into W^ater and of Air into Earth, and again of Water 5 
and Earth into Fire and Air respectively, though possible, 
is more difficult because it involves the change of more 
qualities. For if Fire is to result from Water, both the 
cold and the moist must pass-away : and again, both the 
cold and the dry must pass-away if Air is to result from 
Earth. So, too, if Water and Earth are to result from io 
Fire and Air respectively — both qualities must change. 

This second method of coming-to-be, then, takes a longer 
time. But (iii) if one quality in each of two ' elements ' 
pass-away, the transformation, though easier, is not re- 
ciprocal. Still, from Fire phis Water there will result 
Earth and^ Air, and from An phis Earth Fire and^ Water. 
For there will be Air, when the cold of the Water and the 15 
dry of the Fire have passed-away (since the hot of the 
latter and the moist of the former are left) : whereas, when 
the hot of the Fire and the moist of the Water have passed- 
away, there will be Earth, owing to the survival of the dry 
of the Fire and the cold of the Water. So, too, in the same 
way. Fire and Water will result from Air phis Earth. For 
there will be Water, when the hot of the Air and the dry 20 

^ Aristotle has shown that, by the conversion of a single quality in 
each case, Fire is transformed into Air, Air into Water, Water into 
Earth, and Earth into Fire. This is a cycle of transformations. 
Moreover, the ' elements ' have been taken in their natural consecutive 
series, according to their order in the Cosmos. 

2 sc. alternatively. ^ ^^^ alternatively. 



331^ DE GENERATIONE ET CORRUPTIONE 

of the Earth have passed-away (since the moist of the 
former and the cold of the latter are left) : whereas, when 
the moist of the Air and the cold of the Earth have passed- 
away, there will be Fire, owing to the survival of the hot of 
the Air and the dry of the Earth — qualities essentially 
constitutive of Fire. Moreover, this mode of Fire's coming- 

25 to-be is confirmed by perception. For flame is par ex- 
cellence Fire : but flame is burning smoke, and smoke con- 
sists of Air and Earth. 

No transformation, however, into any of the ' simple ^ 
bodies can result from the passing-away of one elementary 
quality in each of two * elements ' when they are taken in 
their consecutive order,^ because either identical or contrary 

30 qualities are left in the pair : but no * simple * body can be 
formed either out of identical, or out of contrary^ qualities. 
Thus no * simple ' body would result, if the dry of Fire and 
the moist of Air were to pass-away : for the hot is left in 
both. On the other hand, if the hot pass-away out of both, 
the contraries — dry and moist — are left. A similar result 
will occur in all the others too : for all the consecutive 
'elements' contain one identical, and one contrary, quality.^ 

35 Hence, too, it elearly follows that, when one of the con- 
secutive ' elements ' is transformed into one, the coming-to- 
be is effected by the passing-away of a single quality : 
whereas, when two of them are transformed into a third, 
more than one quality must have passed-away.^ 
332^ We have stated that all the ' elements ' come-to-be out 
of any one of them; and we have explained the manner in 
which their mutual conversion takes place. Let us never- 5 
theless supplement our theory by the following speculations 
concerning them. 

^ Cf. above, note on 331^4. 

^ If the 'elements' are taken in their natural order, Water (e.g.) is 
' consecutive ' to Plarth, and Air to Water. Water is moist and cold. 
It shares its 'cold' with Earth and its 'moist' with Air : its 'moist' is 
contrary to Earth's ' dry ', and its ' cold ' is contrary to Air's ' hot '. 

^ If, e.g., PMre pltcs Air are to be transformed into Water or into 
Earth, it is not enough that a single quality should be eliminated from 
each of the generating pair: for this would leave either two 'hots' or 
a 'dry' and a 'moist' (cf. 33i''26-33). Either Fire's 'dry' or Air's 
'moist' must be eliminated: and, i?i additio?t, the 'hot' of one must 
be eliminated and the ' hot ' of the other be converted into ' cold '. 



BOOK II. 5 332' 

If Water, Air, and the like are a * matter ' of which the 5 
natural bodies consist, as some thinkers in fact believe, 
these ' elements ' must be either one, or two, or more. Now 
they cannot all of them be one— they cannot, e. g., all be 
Air or Water or Fire or Earth — because ^ Change is into 
contraries '} For if they all were Air, then (assuming Air 
to persist) there will be 'alteration' instead of coming-to-be. 
Besides, nobody supposes a single ' element ' to persist, as 
the basis of all, in such a way that it is Water as well as Air 10 
(or any other ' element ') at the same time. So there will be 
a certain contrariety, i. e. a differentiating quality : ^ and 
the other member of this contrariety, e. g. heat, will belong 
to some other 'element', e.g. to Fire. But Fire will 
certainly not be 'hot Air'. For a change of that kind^ 
(a) is ' alteration ', and {b) is not what is observed. More- 
over {c) if Air is again to result out of the Fire, it will do 
so by the conversion of the hot into its contrary : this 15 
contrary, therefore, will belong to Air, and Air will be 
a cold something : hence it is impossible for Fire to be 'hot 
Air', since in that case the same thing will be simultaneously 
hot and cold. Both Fire and Air, therefore, will be some- 
thing else which is the same; i.e. there will be some 
'matter', other than either, common to both. 

The same argument applies to all the 'elements', proving 
that there is no single one of them out of which they all 20 
originate. But neither is there, beside these four, some 
other body from which they originate — a something inter- 
mediate, e. g., between Air and Water (coarser than Air, 
but finer than Water), or between Air and Fire (coarser 
than Fire, but finer than Air). For the supposed ' inter- 
mediate ' will be Air and Fire when a pair of contrasted 
qualities is added to it : but, since one of every two con- 
trary qualities is a ' privation ', the ' intermediate ' never 
can exist — as some thinkers assert the ' Boundless ' or the 25 
' Environing ' exists — in isolation.* It is, therefore, equally 

^ For this ' law of nature ', cf. Physics 224* 21 — 226^ 17. 

^ If Air is to 'alter' into (e.g.) Fire, we must assume a pair of 
contrasted differentiating qualities, and assign one to Fire and the 
other to Air. 

^ i. e. Air becoming Fire by being heated. 

'' i. e. bare of all qualities. The ' Boundless ' was criticized above, 



332^ DE GENERATIONE ET CORRUPTIONE 

and indifferently any one of the 'elements', or else it is 
nothing. 

Since, then, there is nothing — at least, nothing perceptible 
— prior to these,^ they must be all.^ That being so, either 
they must always persist and not be transformable into one 
another : or they must undergo transformation — either all 
30 of them, or some only (as Plato wrote in the Timaeus)? 
Now it has been proved before* that they must undergo 
reciprocal transformation. It has also been proved ^ that 
the speed with which they come-to-be, one out of another, 
is not uniform — since the process of reciprocal transforma- 
tion is relatively quick between the ' elements ' with a 
* complementary factor ', but relatively sloiv between those 
which possess no such factor. Assuming, then, that the 
contrariety, in respect to which they are transformed, is 
35 one, the 'elements' will inevitably be two : for it is 'matter' 
that is the ' mean ' between the two contraries, and matter 
332^ is imperceptible and inseparable from them.^ Since, how- 
ever, the * elements ' are seen to be more than two, the 
contrarieties must at the least be two. But the contra- 
rieties being two, the 'elements' must be four (as they 
evidently are) and cannot be three : for the ' couplings ' are 
four, since, though six are possible,'^ the two in which the 
5 qualities are contrary to one another cannot occur. 

These subjects have been discussed before ^ : but the 
following arguments will make it clear that, since the 
'elements' are transformed into one another, it is impossible 
for any one of them — whether it be at the end or in the 
middle^ — to be an 'originative source' of the rest. There 

329*8-13: there too Aristotle attributes the conception to 'some 
people ', without mentioning Anaximander by name. 

* sc. Earth, Air, Fire, and Water. 

^ i.e. all the 'simple' bodies there are. '^ Cf. Tiinaetis 54b-d. 

" Cf. above, 331-'^ 12-20. ^ Cf. above, 331^22 ff. 

^ One contrariety produces two 'elements' only: for npcarr] v\t] has 
no separate subsistence and does not constitute a t/tird 'element' 
alongside of its two contrary informations. Perhaps, however, we 
ought to translate: 'for the supposed "intermediate" is nothing but 
"matter", and that is imperceptible and incapable of separate 
existence.' 

'^ i. e. mathematically ' possible '. 

^ Cf. above, II. 2 and 3. 

° i.e. at either end, or in the middle, of the 'natural series' of the 
' elements '. 



BOOK II. 5 332 

can be no such ' originative element ' at the ends : for all of 
them would then be Fire or Earth, and this theory amounts 
to the assertion that all things^ are made of Fire or Earth. 
Nor can a *■ middle-element ' be such an 'originative source' 10 
— as som^e thinkers suppose that Air is transformed both 
into Fire and into Water, and Water both into Air and into 
Earth, while the 'end-elements' are not further transformed 
into one another. For the process must come to a stop, 
and cannot continue ad infiniticni in a straight line in either 
direction, since otherwise an infinite number of contrarieties 
would attach to the single 'element'. Let E stand for 15 
Earth, W for Water, A for Air, and F for Fire. Then 
(i) since A is transformed into F and W. there will be a 
contrariety belonging to A F. Let these contraries be white- 
ness and blackness. Again (ii) since A is transformed into 
W, there will be another contrariety - : for W is not the 
same as F. Let this second contrariety be dryness and 
moistness, D being dryness and ^I moistness. Now if, 20 
when A is transformed into W, the ' white ' persists. Water 
will be moist and white: but if it does not persist, Water 
will be black since change is into contraries. Water, there- 
fore, must be either white or black. Let it then be the 
first. On similar grounds, therefore, D (dryness) will also 
belong to F. Consequently F (Fire) as well as Air will be 
able to be transformed into Water : for it has qualities 25 
contrary to those of Water, since Fire was first taken to be 
black and then to be dry, while Water was moist and tJien 
showed itself white. Thus it is evident that all the ' elements ' 
will be able to be transformed out of one another ; and that, 
in the instances we have taken, E (Earthj also will contain 
the remaining two '' complementary factors ', viz. the black 30 
and the moist (for these have not yet been coupled). 

We have dealt with this last topic before the thesis we 
set out to prove.^ That thesis — viz. that the process cannot 
continue ad infinittim — will be clear from the following 
considerations. If Fire (which is represented by Y) is not 

^ Or perhaps 'that all the "elements'" result from Fire or Earth by 
"alteration"' — a view which Aristotle has already refuted (cf. 332=* 
6-20). 

^ sc, belonging to AW. ^ Cf. above, 332^ 12-13. 



332^ DE GENERATIONE ET CORRUPTIONE 

to revert, but is to be transformed in turn into some other 
' element ' (e. g. into Q), a new contrariety, other than those 

35 mentioned, will belong to Fire and Q : for it has been 
333^ assumed that Q is not the same as any of the four, E W 
A and F. Let K, then, belong to F and Y to Q. Then K 
will belong to all four, E W A and F : for they are trans- 
formed into one another. This last point, however, we may 
admit, has not yet been proved : but at any rate it is clear 
that if Q is to be transformed in turn into yet another 
5 ' element \ yet another contrariety will belong not only to 
Q but also to F (Fire). And, similarly, every addition of 
a new ' element ' will carry with it the attachment of a new 
contrariety to the preceding ' elements '. Consequently, if 
the * elements ' are infinitely many, there will also belong to 
the single ' element ' an infinite number of contrarieties. But 
if that be so, it will be impossible to define any 'element ' : 
impossible also for any to come-to-be. For if one is to 
result from another, it will have to pass through such a vast 

10 number of contrarieties — and indeed even more than any 
determinate number. Consequently (i) into some ' ele- 
ments ' transformation will never be effected — viz. if the 
intermediates are infinite in number, as they must be if the 
'elements ' are infinitely many : further (ii) there will not even 
be a transformation of Air into Fire, if the contrarieties are 
infinitely many: moreover (iii) all the 'elements' become one. 
For all the contrarieties of the ' elements ' above F m.ust beloncf 

15 to those below F, and vice versa : hence they will all be one. 

As for those who agree with Empedokles that the g 
' elements ' of body are more than one, so that they are not 
transformed into one another ^— one may well wonder in 
what sense it is open to them to maintain that the ' ele- 
ments ' are comparable. Yet Empedokles says ' For these 
20 arc all not only equal . . .' ^ 

If (i) it is meant that they are comparable in their amount, 
all the ' comparables ' must possess an identical something 
whereby they arc measured. If, e. g., one pint of Water 

^ i.e. so that the 'elements' are genuinely or irreducibly 'many'. 
The theory of Junpedokles is directly opposed to the theory Aristotle 
has been maintaining. 

"^ Empedokles, fr. 17, 1. 27 (Diels, p. 179). 



BOOK II. 6 333^ 

yields ten of Air, both are measured by the same unit ; 
and therefore both were from the first an identical some- 
thing. On the other hand, suppose (ii) they are not 'com- 
parable in their amount ' in the sense that so-much of the 
one yields so-much of the other, but comparable in 'power 
of action'^ (a pint of Water, e.g., having a power of cooling 25 
equal to that of ten pints of Air) ; even so, they are ' com- 
parable in their amount ', though not qua ' amount ' but qica 
'so-much power '.^ There is also (iii) a third possibility. 
Instead of comparing their powers by the measure of their 
amount, they might be compared as terms in a 'correspon- 
dence': e.g.,/ as X is hot, so correspondingly j is white'. 
But ' correspondence ', though it means equality in the 30 
qtmntum, means similarity^ in a quale. Thus it is mani- 
festly absurd that the 'simple' bodies, though they are not 
transformable, are comparable not merely as ' correspond- 
ing ', but by a measure of their powers ; i. e. that so-much 
Fire is comparable with many-times-that-amount of Air, as 
being ' equally ' or ' similarly ' hot. For the same thing, if 
it be greater in amount, will, since it belongs to the same 
kind,* have its ratio correspondingly increased. 

A further objection to the theory of Empedokles is that 35 
it makes even growth impossible, unless it be increase by 
addition. For his Fire increases by Fire : ' And Earth 333^ 
increases its own frame and Ether increases Ether.' ^ 
These, however, are cases of addition : but it is not by 
addition that growing things are believed to increase. And 
it is far more difficult for him to account for the coming-to- 
be which occurs in nature. For the things which come-to- 5 
be by natural process all exhibit, in their coming-to-be, 
a uniformity either absolute or highly regular : while any 

^ Cf. above, 327^31, 328^28-31 ; below, 334^8-30. 

- i.e. we are comparing the amcmnts of cooling e?iergy possessed by 
one pint of Water and ten pints of Air respectively. 

^ i. e. only ' similarity '. Empedokles might have said the ' elements ' 
were all analogous qx similar without inconsistency: but he asserts 
that they are egtcal, i. e. quantitatively comparable (and therefore, 
ultimately, transformable). 

* sc. as the thing of less amount with which it is being compared. 

^ Cf. Empedokles, fr. 37 (Diels, p. i86). By aWi^p Empedokles 
means Air (not Fire) as Aristotle recognizes elsewhere : perhaps, 
therefore, the words ' Fire increases by Fire ' are a paraphrase of 
a verse now lost. 



333^ DE GENERATIONE ET CORRUPTIONE 

exceptions — any results which are in accordance neither 
with the invariable nor with the general rule — are products 
of chance and luck. Then what is the cause determining 
that man comes-to-be from man, that wheat (instead of an 
olive) comes-to-be from wheat, either invariably or gener- 
ally? Are we to say 'Bone comes-to-be if the "elements" 
be put together in such-and-such a manner'? For, accord- 

lo ing to his own statements, nothing comes-to-be from their 
' fortuitous consilience ', but only from their ' consilience ' 
in a certain proportion. What, then, is the cause of this 
proportional consilience? Presumably not Fire or Earth. 
But neither is it Love and Strife : for the former is a cause 
of ' association ' only, and the latter only of ' dissociation '. 
No : the cause in question is the essential nature of each 
thing — not merely (to quote his words) ' a mingling and 

15 a divorce of what has been mingled'.^ And c/iance, not 
propo7'tion, ' is the name given to these occurrences ' : ^ for 
things can be ' mingled ' fortuitously. 

The cause, therefore, of the coming-to-be of the things 
which owe their existence to nature is that they are in such- 
and-such a determinate condition : ^ and it is this which con- 
stitutes the 'nature' of each thing — a 'nature'about which he 
says nothing. What he says, therefore, is no explanation 
of ' nature '.* Moreover, it is this which is both ' the excel- 
lence' of each thing and its 'good' : whereas he assigns the 

20 whole credit to the 'mingling'.^ (And yet the '■elements^ 
at all events are 'dissociated' not by Strife, but by Love: 
since the ' elements ' are by nature prior to the Deity, and 
they too are Deities.) ^ 

Again, his account of motion is vague. For it is not an 
adequate explanation to say that ' Love and Strife set things 

^ Cf. Empedokles, fr. 8 (Diels, p. 175). The same fragment is 
quoted above, 314^7-8. 

"^ Aristotle appears to be parodying the last line of Empedokles, fr. 8. 

^ i.e. that they are compounds produced by the consilience of their 
constituents in a certain proportion. 

^ i. e. ]Cmpedokles' poem, in spite of its title (rie/ji (puaeoa), tells us 
nothing about nature. 

•' (C{.Met<;ph. 984''32 - 985=^ lo. 

^ This sentence is a belated criticism of the functions Empedokles 
attributed to Love and Strife : perhaps we ought to read it after alriov 
(above, ^13). The 'Deity' is the 'Sphere': cf. Empedokles. fr. 27, 
28, 29 (Diels, pp. 183-184). 



BOOK 11. 6 333^ 

moving ', unless the very nature of Love is a movement of 
this kind and the very nature of Strife a movement of that 
kind. He ought, then, either to have defined or to have 25 
postulated these characteristic movements, or to have 
demonstrated them — whether strictly or laxly or in some 
other fashion. Moreover, since [a) the ' simple ' bodies 
appear to move "'naturally' as well as by compulsion, i.e. in 
a manner contrary to nature (fire, e. g., appears to move 
upwards without compulsion, though it appears to move by 
compulsion downwards) ; and since {b) what is ' natural ' is 
contrary to that which is due to compulsion, and movement 
by compulsion actually occurs ; ^ it follows that ' natural 
movement ' can also occur in fact. Is this^ then, the move- 30 
ment that Love sets going ? No : for, on the contrary, the 
'- natural movement ' moves Earth downwards and resembles 
'dissociation', and Strife rather than Love is its cause — so 
that in general, too, Love rather than Strife would seem 
to be contrary to nature. And unless Love or Strife is 
actually setting them in motion, the ' simple ' bodies them- 
selves have absolutely no movement or rest. But this is 35 
paradoxical : and what is more, they do in fact obviously 
move.^ For though Strife ' dissociated ',^ it was not by 334^ 
Strife that the " Ether ' was borne upwards. On the con- 
trary, sometimes he attributes its movement to something 
like chance (' For thus, as it ran, it happened to meet them 
then, though often otherwise ' ^), while at other times he 
says it is the nattire of Fire to be borne upwards, but ' the 
Ether ' (to quote his words) ' sank down upon the Earth 5 
with long roots '.^ With such statements, too, he combines 
the assertion that the Order of the World is the same now^ 
in the reign of Strife, as it was formerly in the reign of 
Love. What, then, is the ' first mover' of the 'elements ' ? 
What causes their motion? Presumably not Love and 
Strife : on the contrary, these are causes of a particular 
motion, if at least we assume that ' first mover ' to be an 
' originative source '.® 

^ i.e. according to Empedokles himself. 

^ i. e. according to Empedokles' own statements. 

' i. e. though Strife initiated the disintegration of the Sphere. 

* Cf. Empedokles, fr. 53 (Diels, p. 189). 

^ Cf. fr. 54, ibid. ^ sc. a first cause of motion in general. 



334* DE GENERATIONE ET CORRUPTIONE 

lo An additional paradox is that the soul should consist of 
the ' elements ', or that it should be one of them. How 
are the soul's 'alterations^ to take place? How, e.g., is 
the change from being musical to being unmusical, or how 
is memory or forgetting, to occur? For clearly, if the 
soul be Fire, only such modifications will happen to it as 
characterize Fire q?m Fire : while if it be compounded out 
of the ' elements ', only the cor'poreal modifications will 
occur in it. But the changes we have mentioned are none 

15 of them corporeal. 

The discussion of these difficulties, however, is a task 7 
appropriate to a different investigation : ^ let us return to 
the ' elements ' of which bodies are composed. The theories 
that ' there is something common to all the " elements " ', 
and that ' they are reciprocally transformed ', are so related 
that those who accept eit/ier are bound to accept /ke other 
as well. Those, on the other hand, who do not make their 
coming-to-be reciprocal — who refuse to suppose that any 
one of the ' elements ' comes-to-be out of any other taken 

20 singly^ except in the sense in which bricks come-to-be out of 
a wall — are faced with a paradox. How, on their theory, 
are flesh and bones or any of the other compounds to result 
from the ' elements ' taken togethei'- ? 

Indeed, the point we have raised constitutes a problem 
even for those who generate the 'elements^ out of one 
another. In what manner does anything other than, and 
beside, the ' elements ' come-to-be out of them ? Let me - 
illustrate my meaning. Water can come-to-be out of Fire 
and Fire out of Water ; for their stibstrattmi is something 

25 common to them both. But flesh too, presumably, and 
marrow come-to-be out of them. How, then, do such 
things come-to-be ? For {a) how is the manner of their 
coming-to-be to be conceived by those who maintain a theory 
like that of Empedokles? They must conceive it as com- 
position — ^just as a wall comes-to-be out of bricks and 
stones : and the ' Mixture ', of which they speak, will be 
composed cf the ' elements ', these being preserved in it 

^ Cf. de Anima, A. 4 and 5, especially 408^*18-23 and 409''23ff., 
where Aristotle exposes the failure of Empedokles to account for 
the soul. 



BOOK II. 7 334^ 

unaltered but with their small particles juxtaposed each to 3^ 
each. That will be the manner, presumably, in which flesh 
and every other compound results from the ' elements \ 
Consequently, it follows that Fire and Water do not come- 
to-be ' out of any and every part of flesh '. For instance, 
although a sphere might come-to-be out of tJiis part of 
a lump of wax and a pyramid Qut oi some other part, it was 
nevertheless possible for either figure to have come-to-be 
out of either part indifferently : that is the manner of 35 
coming-to-be when ' both Fire and Water come-to-be out 
of any and every part of flesh '. Those, however, w^ho main- 
tain the theory in question, are not at liberty to conceive 334^ 
that ' both come-to-be out of flesh ' in that manner, but only 
as a stone and a brick ' both come-to-be out of a wall ' — 
viz. each out of a different place or part. Similarly {b) 
even for those who postulate a single matter of their 
'elements' there is a certain difficulty in explaining how 
anything is to result from two of them taken together — e.g. 
from ' cold ' and ' hot ', or from Fire and Earth. For if flesh 5 
consists of both and is neither of them, nor again is a ' com- 
position ' of them in w^hich they are preserved unaltered, 
what alternative is left except to identify the resultant of 
the two ' elements ' with their matter ? For the passing- . 
away of either ' element' produces eitJie7' the other -or the 
matter. 

Perhaps we may suggest the following solution, (i) There 
are differences of degree in hot and cold. Although, there- 
fore, when either is fully real without qualification, the other 
wall exist potentially ; yet, when neither exists in the full 10 
completeness of its being, but both by combining destroy 
one another's excesses so that there exist instead a hot 
which (for a ' hot ') is cold and a cold which (for a ' cold ') is 
hot ; then w^hat results from these two contraries will be 
neither their matter, nor either of them existing in its full 
reality without qualification. There will result instead an 
' intermediate ' : and this ' intermediate ', according as it is 
potentially more hot than cold or vice versa, will possess 15 
a power-of-heating that is double or triple its power-of- 
cooling, or otherwise related thereto in some similar ratio. 

F 2 



334'' DE GENERATIONE ET CORRUPTIONE 

Thus all the other bodies will result from the contraries, or 
rather from the ' elements ', in so far as these have been 
' combined ' : while the ' elements ' will result from the con- 
traries, in so far as these ' exist potentially ' in a special 
sense — not as matter ' exists potentially ', but in the sense 
explained above. And when a thing comes-to-be in this 

20 manner, the process is * combination ' ; whereas what comes- 
to-be in the other manner ^ is matter. Moreover (ii) con- 
traries also 'suffer action', in accordance with the disjunc- 
tively-articulated definition established in the early part of 
this work.^ For the actually-hot is potentially-cold and 
the actually-cold potentially-hot; so that hot and cold, 
unless they are equally balanced, are transformed into one 
another (and all the other contraries behave in a similar 

25 way). It is thus, then, that in the first place the * elements ' 
are transformed ; and that (j.n the second place) ^ out of the 
' elements ' there come-to-be flesh and bones and the like — 
the hot becoming cold and the cold becoming hot when 
they^ have been brought to the 'mean'. For at the 
' mean ' is neither hot nor cold. The ' mean ', however, is 
of considerable extent and not indivisible.^ Similarly, it 
is qua reduced to a ' mean ' condition that the dry and the 
moist, as well as the contraries we have used as examples, 

30 produce flesh and bone and the remaining compounds. 

All the compound bodies — all of which exist in the 8 
region belonging to the central body ^ — are composed of all 
the 'simple' bodies. For they all contain Earth because 
every ' simple ' body is to be found specially and most 
abundantly in its own place. And they all contain Water 
35 because {a) the compound must possess a definite outline 

* sc. in the only manner which was taken into account in the 
formulation of the problem at 334^^6-7. ^.^, 

"^ Cf. above, I. 7, where Aristotle explains the precise sense in 
which action-passion is between contraries, and under what conditions 
contraries in 'acting' are themselves 'acted upon' by their patients. 

^ There is no expressed dra (answering to npcoTov in ^24) but it is 
Implied. 

^ sc. these extremes, the completely-hot and the completely-cold. 

^ i. e. the ' mean ' is a stretch, not a point. 

^ Or perhaps ' in the region about the centre '. 



BOOK II. 8 335' 

and Water, alone of the 'simple' bodies, is readily adapt- 335' 
able in shape : moreover {b) Earth has no power of cohesion 
without the moist. On the contrary, the moist is what 
holds it together ; for it would fall to pieces if the moist 
were eliminated from it completely. 

They contain Earth and Water, then, for the reasons we 
have given : and they contain Air and Fire, because these are 
contrary to Earth and Water (Earth being contrary to Air 5 
and Water to Fire, in so far as one Substance can be 
'contrary' to another). Now all compounds presuppose 
in their coming-to-be constituents which are contrary to 
one another : and in all compounds there is contained one 
set of the contrasted extremes.^ Hence the other set ^ 
must be contained in them also, so that every compound 
will include all the 'simple' bodies. 

Additional evidence seems to be furnished by the food 10 
each compound takes. For al] of them are fed by sub- 
stances which are the same as their constituents, and all 
of them are fed by more substances than one. Indeed, 
even the plants, though it might be thought they are 
fed by one substance only, viz. by Water, are fed by 
more than one : for Earth has been mixed with the 
Water. That is why farmers too endeavour to mix before 
watering.^ 

Although food is akin to the matter, that which is fed 15 
is the ' figure ' — i. e. the ' form ' — taken along with the 
matter.^ This fact enables us to understand why, whereas 
all the ' simple ' bodies come-to-be out of one another. Fire 
is the only one of them which (as our predecessors also 
assert) ' is fed '.^ For Fire alone^or more than all the 
rest — is akin to the 'form' because it tends by nature 
to be borne towards the limit. Now each of them naturally 20 
tends to be borne towards its own place : but the ' figure ' 
— i. e. the ' form '■ — of them all is at the limits. 



^ i.e. cold-dry (Earth) and cold-moist- (Water). 

"^ i.e. hot-moist (Air) and hot-dry (Fire). 

^ Plants are nourished naturally by water impregnated with earth 
and artificially by water mixed with manure, which is a kind of earth. 

* Cf. above, 321^16 — 322^33. 

^ Cf. de Vita et ^Torte 469^ 21 ff.. Meteor. 354^33 ff. ; Theophrastos, 
fr. iii. I, § 4 (Wimmer, iii, p. 51). 



335^ DE GENERATIONE ET CORRUPTIONE 

Thus we have explained that all the compound bodies 
are composed of all the ' simple ' bodies. 



Since some things are such as to come-to-be and pass- 9 
25 away, and since coming-to-be in fact occurs in the region 
about the centre, we must explain the number and the nature 
of the ' originative sources ' of all coming-to-be alike : ^ for 
a grasp of the true theory of any universal facilitates the 
understanding of its specific forms. 

The 'originative sources', then, of the things which 
come-to-be. are equal in number to, and identical in kind 
with, those in the sphere of the eternal and primary things. 
30 For there is one in the sense of ^ matter ', and a second in 
the sense of ' form ' : and, in addition, the third ' originative 
source' must be present as well. For the two first are not 
sufficient to bring things into being, any more than they 
are adequate to account for the primary things. 

Now cause, in the sense of material origin, for the things 
which are such as to come-to-be is ' that which can be-and- 
not-be': and this is identical with 'that which can come- 
to-be-and-pass-away ', since the latter, while it is at one 
time, at another time is not. (For whereas some things 
are of necessity, viz. the eternal things, others of necessity 
35 are not. And of these two sets of things, since they cannot 
335^ diverge from the necessity of their nature, it is impossible 
for the first not to be and impossible for the second to be. 
Other things, however, can both be and not be) Hence 
coming-to-be and passing-away must occur within the field 
5 of ' that which can be-and-not-be '. This, therefore, is cause 
in the sense of material origin for the things which are 
such as to come-to-be ; while cause, in the sense of their 
' end ', is their ' figure ' or * form ' — and that is the formula 
expressing the essential nature of each of them. 

But the third ' originative source ' must be present as 
well — the cause vaguely dreamed of by all our predecessors, 
^ Cf. above, 314^2 and 318^25-27. 



BOOK II. 9 335b 

definitely stated by none of them. On the contrary (a) some 
amongst them thought the nature of ' the Forms ' was 10 
adequate to account for coming-to-be. Thus Sokrates in 
the PJiaedo first blames everybody else for having given 
no explanation ; ^ and then lays it down that ' some things 
are Forms, others Participants in the Forms', and that 
'while a thing is said to "be" in virtue of the Form, it 
is said to " come-to-be " qua " sharing in ", to '' pass-away " 
qtia "losing", the Form'. Hence he thinks that 'assuming 15 
the truth of these theses, the Forms imtst be causes both of 
coming-to-be and of passing-away '.^ On the other hand 
{b) there were others who thought ' the matter ' was adequate 
by itself to account for coming-to-be, since ' the movement 
originates from the matter '. 

Neither of these theories, however, is sound. For [a) if the 
Forms are causes, why is their generating activity inter- 
mittent instead of perpetual and continuous — since there 
always are Participants as well as Forms? Besides, in 20 
some instances we see that the cause is other than the 
Form. For it is the doctor who implants health and 
the man of science who implants science, although ' Health 
itself and 'Science itself are as well as the Participants: 
and the same principle applies to everything else that is 
produced in accordance with an art. On the other hand 
{h) to say that ' matter generates owing to its movement ' 25 
would be, no doubt, more scientific than to make such 
statements as are made by the thinkers we have been 
criticizing. For what ' alters ' and transfigures plays 
a greater part ^' in bringing things into being ; and we are 
everywhere accustomed, in the products of nature and 
of art alike, to look upon that which can initiate move- 
ment as the producing cause. Nevertheless this second 
theory is not right either. 

For. to begin with, it is characteristic of matter to suffer 30 
action, i. e. to be moved : but to move, i. e. to act, belongs 
to a different ' power '.^ This is obvious both in the things 

1 Cf. Plato, PJiaedo 96a-99c. ^ Cf. Plato, Phaedo loob-ioi e. 
^ sc. than the Forms. 

* Matter is a hvva\i.i^ in the passive sense ; that which initiates 
movement is a hvva\xi^ in the sense of an active force. Cf. e.g. Meta'ph. 

1046^9-29, 1048^25-^9. 



335^ DE GENERATIONE ET CORRUPTIONE 

that come-to-be by art and in those that come-to-be by 
nature. Water does not of itself produce out of itself 
an animal : and it is the art, not the wood, that makes 
a bed. Nor is this their only error. They make a second 

35 mistake in omitting the more controlling cause : for they 
336^ eliminate the essential nature, i. e. the ' form '. And what 
is more, since they remove the formal cause, they invest 
the forces they assign to the ' simple ' bodies — the forces 
which enable these bodies to bring things into being — with 
too instrumental a character. For ' since ' (as they say) 
'it is the nature of the hot to dissociate, of the cold to 

5 bring together, and of each remaining contrary either to act 
or to suffer action ', it is out of such materials and by their 
agency (so they maintain) that everything else comes-to-be 
and passes-away. Yet (a) it is evident that even Fire is 
itself moved, i. e. suffers action. Moreover (d) their pro- 
cedure is virtually the same as if one were to treat the 
saw (and the various instruments of carpentry) as ' the cause ' 

10 of the things that come-to-be : for the wood 7;ms^ be divided 
if a man saws, i/iust become smooth if he planes, and so on 
with the remaining tools. Hence, however true it may be 
that Fire is active, i. e. sets things moving, there is a further 
point they fail to observe — viz. that Fire is inferior to the 
tools or instruments in the manner in which it sets things 
moving. 

As to our own theory — we have given a general account 
of the causes in an earlier work,^ and we have now explained 
and distinguished the ' matter ' and the ' form '.^ Further, 10 

If since the change which is motion has been proved^ to be 
eternal, the continuity of the occurrence of coming-to-be 
follows necessarily from what we have established : for the 
eternal motion, by causing ' the generator ' ^ to approach 
and retire, will produce coming-to-be uninterruptedly. At 
the same time it is clear that we were also right when, 

20 in an earlier work,^ we called motion (not coming-to-be) 
' the primary form of change '. For it is far more reason- 

' Cf. Physics B. 3-9. •^ Cf. above, 335*32-^7. 

^ Cf. Physics e. 7-9. 

* i. c. the sun, as will appear presently. 

*"' Cf. Physics 26o"^26-26i"26. 



BOOK 11. lo 336^ 

able that what is should cause the coming-to-be of what is 
not, than that what is not should cause the being oiivhat is. 
Now that which is being moved is, but that which is coming- 
to-be is not : hence, also, motion is prior to coming-to-be. 

We have assumed, and have proved,^ that coming-to-be 
and passfng-away happen to things continuously ; and we 25 
assert that motion causes coming-to-be. That being so, it 
is evident that, if the motion be single, l^oth processes cannot 
occur since they are contrary to one another : for it is a law 
of nature that the same cause, provided it remain in the 
same condition, always produces the same effect, so that, 
from a single motion, either coming-to-be or passing-away 
will always result. The movements must, on the contrary, 
be more than one, and they must be contrasted with one 30 
another either by the sense of their motion ^ or by its 
irregularity : ^ for contrary effects demand contraries as 
their causes. 

This explains why it is not the primary motion ^ that 
causes coming-to-be and passing-away, but the motion 
along the inclined circle : ^ for this motion not only possesses 
the necessary continuity, but includes a duality of move- 
ments as well. For if coming-to-be and passing-away are 336^ 
always to be continuous, there must be some body always 
being moved (in order that these changes may. not fail) and 
moved with a duality of movements (in order that both 
changes, not one only, may result). Now the continuity of 
this movement is caused by the motion of the whole : ^ but 
the approaching and retreating of the moving body are 
caused by the inclination.' For the consequence of the 
inclination is that the body becomes alternately remote 5 
and near;^and since its distance is thus unequal, its move- 
ment will be irregular. Therefore, if it generates by ap- 
proaching and by its proximity, it — this very same body — 

^ Cf. above, 3i7^33ff. - Cf. de Caelo 270^32—271^33. 

^ Cf. de Caelo 288^ 13-27 ; Physics 228'^ 15 — 229*6. 

* i. e. the revolution of the Trpwros ovpavos. 

^ i. e. the annual movement of the sun in the ecliptic or zodiac circle. 

^ i.e. the revolution of the npcoros ovpavos (the outermost sphere) 
v^'hich carries along with it all the concentric spheres. 

' i. e. the inclination of the ecliptic to the equator of the outermost 
sphere, which (on Aristotle's theory) is the equator of the universe and 
is in the same plane as the terrestrial equator. 



336^ DE GENERATIONE ET CORRUPTIONE 

destroys by retreating and becoming remote : and if it gener- 
ates by many successive approaches, it also destroys by many 
successive retirements. For contrary effects demand contraries 

10 as their causes ; and the natural processes of passing-away 
and coming-to-be occupy equal periods of time. Hence, 
too, the times — i. e. the lives — of the several kinds of living 
things have a number by which they are distinguished : for 
there is an Order controlling all things, and every time 
(i. e. every life) is measured by a period. Not all of them, 
however, are measured by the same period, but some by 
a smaller and others by a greater one : for to some of them 

15 the period, which is their measure, is a year, while to some 
it is longer and to others shorter. 

And there are facts of observation in manifest agreement 
with our theories. Thus we see that coming-to-be occurs 
as the sun approaches and decay as it retreats ; and we see 
that the two processes occupy equal times. For the dura- 
tions of the natural processes of passing-away and coming- 

20 to-be are equal. Nevertheless it often happens that things 
pass-away in too short a time. This is due to the ' inter- 
mingling ' by which the things that come-to-be and pass- 
away are implicated with one another. For their matter is 
' irregular ', i. e. is not everywhere the same : hence, the 
processes by which they come-to-be must be 'irregular' too, 
i. e. some too quick and others too slow. Consequently the 
phenomenon in question occurs, because the 'irregular' 
coming-to-be of these things is the passing-away of other 
things.^ 

25 Coming-to-be and passing-away will, as we have said, 
always be continuous, and will never fail owing to the cause 
we stated.^ And this continuity has a sufficient reason on 
our theory. For in all things, as we affirm, Nature always 
strives after ' the better '. Now ' being ' (we have explained 
elsewhere " the exact variety of meanings we recognize in 

30 this term) is better than ' not-being ' : but not all things can 
possess ' being ', since they are too far removed from the 
' originative source '. God therefore adopted the remaining 

^ For the reading and interpretation of 336^' 20-24 see my text and 
commentary. 

2 Cf. above, 318* 9 ff. 

'' Cf. e.g. Metaph. 1017^7 ff. 



BOOK II. lo 336^ 

alternative, and fulfilled the perfection of the universe 
by making coming-to-be uninterrupted : for the greatest 
possible coherence would thus be secured to existence, 
because that ' coming-to-be should itself come-to-be per- 
petually ' is the closest approximation to eternal being. 

The cause of this perpetuity of coming-to-be, as we have 
often said, is circular motion : for that is the only motion 337* 
which is continuous. That, too, is why all the other things 
— the things, I mean, which are reciprocally transformed in 
virtue of their * passions ' and their ' powers of action \ e. g. 
the ' simple ' bodies — imitate circular motion. For when 
Water is transformed into Air, Air into Fire, and the Fire 5 
back into Water, we say the coming-to-be ' has completed 
the circle', because it reverts again to the beginning. Hence 
it is by imitating circular motion that rectilinear motion too 
is continuous. 

These considerations serve at the same time to explain 
what is to some people a baffling problem — viz. why the 
'simple' bodies, since each of them is travelling towards its 
own place, have not become dissevered from one another in 10 
the infinite lapse of time. The reason is their reciprocal 
transformation. For, had each of them persisted in its own 
place instead of being transformed by its neighbour, they 
would have got dissevered long ago. They are trans- 
formed, however, owing to the motion with its dual charac- 
ter : ^ and because they are transformed, none of them is 
able to persist in any place allotted to it by the Order.^ 15 

It is clear from what has been said (i) that coming-to-be 
and passing-away actually occur, (ii) what causes them, and 
(iii) what subject undergoes them. But {a) if there is to be 
movement (as we have explained elsewhere, in an earlier 
work ^) there must be something which initiates it ; if there 
is to be movement always, there must always be something 
which initiates it ; if the movement is to be continuous, 
what initiates it must be single, unmoved, ungenerated, and 20 

^ The sun's annual movement, by which it alternately approaches 
and retreats, causes the alternate ascent and descent of Water, Air, 
and Fire. They are ttwis brought into contact, with the result that 
their constitutive contrary qualities act and sufter action reciprocally, 
and the ' simple ' bodies themselves are transformed. 

^ Cf. above, 336'^ 12. 

^ Physics 255t»3i — 260^ 10. Cf. also Metaph. 1072^ 19 — 1074^ 14. 



337^ DE GENERATIONE ET CORRUPTIONE 

incapable of ' alteration ' ; and if the circular ^ movements 
are more than one, their initiating causes ^ must all of them, 
in spite of their plurality, be in some way subordinated 
to a single ' originative source '. Further {b) since time is 
continuous, movement must be continuous, inasmuch as 
there can be no time without movement. Time, therefore, 
is a ' number ' ^ of some continuous movement — a ' number ', 

25 therefore, of the circular movement, as was established in 
the discussions at the beginning.^ But {c) is movement ° 
continuous because of the continuity of that which is moved, 
or because that in which the movement occurs (I mean, e. g., 
the place or the quality) is continuous? The answer 
must clearly be 'because that which is moved is continuous'. 
(For how can the quality be continuous except in virtue of 
the continuity of the thing to which it belongs ? But if the 
continuity of 'that in which' contributes to make the move- 

30 ment continuous, this is true only of ' the place in which ' ; 
for that has ' magnitude ' in a sense.) But {d) amongst 
continuous bodies which are moved, only that which is 
moved in a circle is ' continuous ' in such a way that it 
preserves its continuity with itself throughout the movement. 
The conclusion therefore is that this is what produces 
continuous movement, viz. the body which is being moved 
in a circle ; and its movement makes time continuous. 

Wherever there is continuity in any process (coming-to- II 

35 be or ' alteration ' or any kind of change whatever) we 

337^ observe ' consecutiveness', i.e. this coming-to-be after that 

without any interval. Hence we must investigate whether, 

amongst the consecutive members, there is any whose future 

being is necessary ; or whether, on the contrary, every one 

' i. e. the supposed continuous movements which, qua continuous, 
must be circular. 

^ I follow Philoponos and Pacius in referring ravm^ ('^21) to the 
(ipX"-'- which the circular movements imply. 

' i.e. time is that which is munerable {api6fx(')s — to apidfiovfievov or 
TO (]piOfj.rjT6u, not <u cifndfxovnev) in continuous movement : cf. Physics 
219^1-8. 

'^ sc. at the beginning of Aristotle's 'Philosophy of Nature': 
cf. Physics 2I7''29— 224=^ 17. 

" Aristotle uses Kivqais in its general sense, in which it includes 
aWoicjais and ov^rja-is as well as cf)opd, but he is thinking primarily 

of (f)(ipn. 



BOOK II. II 337'' 

of them may fail to come-to-be. For that some of them 
may fail to occur, is clear, (a) We need only appeal to the 
distinction between the statements ' x will be ' and ' x is 
about to . . .', which depends upon this fact. For if it be 
true to say of x that it ' will be ', it must at some time be 5 
true to say of it that ' it is ' : whereas, though it be true to 
say of X now that * it is about to occur ', it is quite possible 
for it not to come-to-be — thus a man might not walk, 
though he is now ' about to ' walk. And {b) since (to 
appeal to a general principle) amongst the things which 
' are' some are capable also of ' not-being', it is clear that 
the same ambiguous character will attach to them no 
less when they are coming-to-be : in other words, their 
coming-to-be will not be necessary. 

Then are all the things that come-to-be of this contingent 10 
character ? Or, on the contrary, is it absolutely necessary 
for some of them to come-to-be ? Is there, in fact, a dis- 
tinction in the field of ' coming-to-be ' corresponding to the 
distinction, within the field of ^ being ', between things that 
cannot possibly ' not-be ' and things that can ' not-be ' ? 
For instance, is it necessary that solstices shall come-to-be, 
i. e. impossible that they should fail to be able to occur? 

Assuming that the antecedent must have come-to-be if 
the consequent is to be (e. g. that foundations must have 15 
come-to-be if there is to be a house : clay, if there are to 
be foundations), is the converse also true ? If foundations 
have come-to-be, must a house come-to-be ? The answer 
seems to be that the necessary nexics no longer holds, unless 
it is 'necessary' for the consequent (as well as for the ante- 
cedent)^ to come-to-be — 'necessary' absolutely. If that be 
the case, however, *a house must come-to-be if foundations 
have come-to-be ', as well as vice versa. For the antece- 
dent was assumed to be so related to the consequent that, 
if the latter is to be, the antecedent must have come-to-be 
before it. If, therefore, it is necessary that the consequent 20 • 
should come-to-be, the antecedent also must have come-to- 
be : and if the antecedent has come-to-be, then the conse- 

^ Cf. above, ^ 14-15: the coming-to-be of the antecedent was 
conditionally necessary, i.e. necessarily presupposed in the being of 

the consequent. 



337^ DE GENERATIONE ET CORRUPTIONE 

quent also must come-to-be — not, however, because of the 
antecedent, but because the future being of the consequent 
was assumed as necessary. Hence, in any sequence, when 
the being of the consequent is necessary, the nexus is 
reciprocal — in other words, when the antecedent has come- 

25 to-be the consequent must ahvays come-to-be too. 

Now (i) if the sequence of occurrences is to proceed ad 
infiniULni 'downwards '} the coming-to-be of any determi- 
nate ' this' amongst the later members of the sequence will not 
be absolutely, but only conditionally, necessary. For it will 
always be necessary that some other ^ member shall have 
come-to-be before * this ' as the presupposed condition ot 
the necessity that ' this ' should come-to-be : consequently, 
since what is ' infinite ' has no ' originative source ', neither 
will there be in the infinite sequence any ' primary ' member 
which will make it ' necessary ' for the remaining members 
to come-to-be.^ 

30 Nor again (ii) will it be possible to say with truth, even 
in regard to the members of a limited sequence, that it is 
* absolutely necessary ' for any one of them to come-to-be. 
We cannot truly say, e. g., that ' it is absolutely necessary 
for a house to come-to-be when foundations have been laid ' : 
for (unless it is always necessary for a house to be coming- 
to-be) we should be faced with the consequence that, when 
foundations have been laid, a thing, which need not always 
be, must always be. No : if its coming-to-be is to be 

35 ' necessary ', it must be ' always ' in its coming-to-be. For 
what is ' of necessity ' coincides with what is ' always ', 
338^ since that which 'must be' cannot possibly 'not-be'. Hence 
a thing is eternal if its * being ' is necessary : and if it is 
eternal, its ' being ' is necessary. And if, therefore, the 
' coming-to-be ' of a thing is necessary, its ' coming-to-be ' 
is eternal ; and if eternal, necessary. 

It follows that the coming-to-be of anything, if it is 
. r absolutely necessary, must be cyclical — i. e. must return 

^ i. e. so that effect luill succeed effect endlessly. 

^ i. e. some other still later member of the sequence. 

' i. e.' the infinite sequence will not contain any absolutely necessary 
member which will serve as the ground of the conditional necessity of 
the other members. The 'primary' member or apx^? ii^ the sequence 
proceeding ad infinitum ' downwards ', would have to be a Ti\os — 
i.e. an absolutely necessary 'end-event'. 



BOOK II. II 338* 

upon itself. For coming-to-be must either be limited or 
not limited : and if not limited, it must be either rectilinear 
or cyclical. But the first of these last two alternatives is 
impossible if coming-to-be is to be eternal, because there 
could not be any ' originative source ' whatever in an infinite 
rectilinear sequence, whether its members be taken ' down- 
wards ' (as future events) or ' upwards ' (as past events). 
Yet coming-to-be must have an ' originative source ' (if it is 
to be necessary and therefore eternal),^ nor can it be eternal 10 
if it is limited.^ Consequently it must be cyclical. Hence 
the nextis must be reciprocal. By this I mean that the 
necessary occurrence of ' this ' involves the necessary occur- 
rence of its antecedent : and conversely that, given the 
antecedent, it is also necessary for the consequent to come- 
to-be. And this reciprocal nexus will hold continuously 
throughout the sequence : for it makes no difference 
whether the reciprocal 7iextLs, of which we are speaking, is 
mediated by two, or by many, members. 

It is in circular movement, therefore, and in cyclical 15 
coming-to-be that the ' absolutely necessary ' is to be found. 
In other words, if the coming-to-be of any things is cyclical, 
it is ' necessary ' that each of them is coming-to-be and has 
come-to-be : and if the coming-to-be of any things is 
' necessary ', their coming-to-be is cyclical. 

The result we have reached is logically concordant with 
the eternity of circular motion, i.e. the eternity of the 
revolution of the heavens (a fact which approved itself on 
other and independent evidence),^ since precisely those 
movements which belong to, and depend upon, this eternal 338^ 
revolution ' come-to-be ' of necessity, and of necessity * will 
be '. For since the revolving body is always setting some- 
thing else in motion, the movement of the things it moves 
must also be circular. Thus, from the being of the ' upper 
revolution ' it follows that the sun revolves in this determi- 
nate manner ; and since the sun revolves tlms, the seasons 
in consequence come-to-be in a cycle, i. e. return upon 
themselves ; and since they come-to-be cyclically, so in 5 

^ A clause to this effect seems to have dropped out after apxh^ 
in '^ 10. 

^ On the reading and interpretation see my text and commentary. 
^ Cf. Physics 0. 7-9. 



338^ DE GENERATIONE ET CORRUPTIONE 

their turn do the things whose coming-to-be the seasons 
initiate. 

Then why do some things manifestly come-to-be in this 
cyclical fashion (as, e. g., showers and air, so that it must 
rain if there is to be a cloud and, conversely, there must be 
a cloud if it is to rain), while men and animals do not 
' return upon themselves ' so that the same individual 
10 comes-to-be a second time (for though your coming-to-be 
presupposes your father's, his coming-to-be does not pre- 
suppose yours) ? Why, on the contrary, does this coming- 
to-be seem to constitute a rectilinear sequence ? 

In discussing this new problem, we must begin by 
inquiring whether all things ' return upon themselves ' in 
a uniform manner; or whether, on the contrary, though 
in some sequences what recurs is numerically the same, in 
other sequences it is the same only in species} In conse- 
quence of this distinction, it is evident that those things, 
whose ' substance ' — that which is undergoing the process — 
15 is imperishable, will be numerically, as well as specifically, 
the same in their recurrence : for the character of the pro- 
cess is determined by the character of that which undergoes 
it. Those things, on the other hand, whose * substance ' is 
perishable (not imperishable) must ' return upon themselves ' 
in the sense that what recurs, though specifically the same, 
is not the same numerically. That is why, when Water 
comes-to-be from Air and Air from Water, the Air is the 
same 'specifically', not 'numerically': and if these too 
recur numerically the same,^ at any rate this does not 
happen with things whose ' substance ' comes-to-be — whose 
' substance ' is such that it is essentially capable of not- 
being. 

^ i.e. in some cycles the same individual eternally recurs : in others 
the same species or specijic form is eternally represented in the succes- 
sion of its perishing individual embodiments. 

^ As, e.g., a follower of Empedokles would maintain. 



Printed in England at the Oxford University Press 



INDEX 



14-32 = 314-338 



Action-passion 15*^5-6 ; 22^6-29: 



23^6-25; 23" I — 27*29 



im- 



plied in ' combination' 28* 18- 
35; 28^16-22 — conflicting- 
traditional theories 23^1 — 24^ 
24 — erroneous theories of 
its mechanism 24^' 25 — 26^ 28 

— Aristotle's theory 23^29 — 24^^ 
22; 26^29 — 27*29 

Agents, comp. with ' movers ' 23* 
12-22 ; 24* 24-'^ 13 —'first' 
)( ' last ' 24a 26-^ 4 (cf. 24^ 27) 

— and patients are identical in 
kind but contrary in species 23^ 
29—24=^ 14 

Air, 'hot-moist', 'a sort of aqueous 
vapour ', 30^ 4 — par excel- 
lence ' moist '31*5 — contrary 
to Earth 31*2; 35^5-6 — is 
an intermediate ' element ' 30^ 
34—31*1 (cf. 30^13-19; 32b 
10-12) — and Wind are less 
perceptible but 'more real ' than 
Earth 18^29-33 (cf. 19^ 20-21) 

Alteration (aXAot'coo-tf), defined 19^ 
10-14 (cf. 14^17—15^3; 31* 
9-10) — afactofobsen-ation 
14^13-15 (cf. 27*16-22) )( com- 
ing-to-be and passing-away 14* 
6ff. > I5*26ff. ; 17*17-27; 19^ 
6 — 20*2 — impossible on the 
theory of Demokritos 27* 15-22 

Anaxagoras, quoted 14* 14-15 

— criticized 14* 13-16 (?cf. 27b 
19-22) — his 'elements ' = the 
'homoeomeries ' 14*18-20; 14* 



28- 



his theory comp. 



with that of Leukippos and 
Demokritos 14* 17-24 )( that 
of Empedokles 14*24-'^ i 

(Anaximander) see s.v. 'Bound- 
less ' 

Aristotle criticizes Anaxagoras 14* 
13-16 (?cf, 27b 19-22J — the 
' Boundless ' 29* 8-13 ; 32* 20- 
26 — Demokritos 23^ 18-24 

— the Eleatics 25* 13-23 

— Empedokles 14^4 — 15*25 ; 
25^ 15-25 ; 26^6-28 ; 33* 16- 



34' 



Leukippos and Demo- 



kritos 15^6—17*31; 25^34— 
26^ 6 — Plato 15* 29-33 ; 

15^30—16*14; 29*13-24 
^ (Pythagorean) Materialists 
35^ 24 — 36* 12 — ' Sokrates 
in the Phaedo '35^ 9-24 
discusses ' action-passion ' 23^' i 

— 27* 29 — ' indivisible 
magnitudes ' 15^24 — 17* 17 

— ' combination ' 27* 30—28^ 
22 — 'contact' 22^21 — 23* 
34 — growth 20* 8 — 22* 33 

distinguishes 'unqualified' from 
' quahfied ' coming-to-be and 
passing-away 17* 32 — 19^ 5 

— 'substantial 'from other forms 
of change 19^ 6 — 20* 2 

his conception of degrees of 
reality, cf. 18^14— 19*3 — of 
fnateria prima 20^ 14-25 ; 29* 
24-35; (cf. 19*29-^4) 
See also s. vv. Cause, Elements, 
Matter, Motion 

Assimilation (in nutrition and 
growth) 21^ 35 — 22* 16 

' Association ' and ' dissociation ' 
)( coming-to-be and passing- 
away 17* 17-22 — facilitate 
coming-to-be and passing-away 
17* 27-29 — attributed by 

Empedokles to ' Love ' and 
' Strife ' 33^^ 12-13 ; 33'^ 20—34* 
9; (cf. 15M-25) 

Black and white = differences 
characterizing the 'elements' of 
Empedokles 14^17-26 

' Boundless ', the (Anaximander) 
29* 8-13 ; 32* 20-26 — a 

body intermediate between Air 
and Fire 28*^34—29*1, between 
Air and Water or Air and Fire 
32* 20-22 

Brittle and viscous 29^ 20 ; 29*^ 
32-34; 30*4-7 

Categories, the 17^ 6, 9, 26 ; 19* 1 1 

Cause, material )( efficient 18'* i- 

8 — final, not ' active ' 24^ 

14-18 efficient cause of 



INDEX 



'alteration' 21^6-10 —of 

growth 21^6-10; 22^ 10-13; 

22» 29-33 

causes of coming-to-be and of 
its perpetuity, mate7-ial, formal^ 
efficient 35* 28-32 — ma- 

terial 18* 9—19^ 4 ; 35^ 32-^ 5 
— formal 35^^ 5-7 — fi7ial 
35^ 5-7 (cf. 36^25-34) —effi- 
cient id^ 17-21 ] 35*30-32; 

35^7—37^33 

Chance 33^4-16; 34^2-3 

Coarse and fine 29^ 20 ; 29^ 32 — 
30^4 

' Cold 'j the, defined 29^^ 29-30 — 
a ' power to act ' 29^^ 24-26 (cf. 
30''^ 12-13) See also s.v. Hot- 
cold 

Colour, its reality denied by 
Demokritos 16^ 1-2 

Columns, the contrasted 19^ 15 
(cf. 18^ 14-18) 

Combination {fxi^ts) 15^4; 22^^ 8 ; 
22^21-29; 24^32-35; 27^ 
30—28^ 22 — defined 28*^ 22 

— implies action-passion 28^ 
18-35 ; 28^ 16-22 • )( coming- 
to-be and passing-away 27^ 6- 
31 — implied in coming-to- 
be 34^8-30 )( mechanical 
mixture 27^ 32— 28=^ 17 (cf. 28^ 
17-20; 34^23—^7) — of tin 
and bronze 28'^ 6-13 

Coming-to-be and passing-away 
)( 'alteration' 14* 6 ff. ; 15^ 
26 ff.; 17*17-27; 19^6—20^2 
)( ' association ' and ' dissocia- 
tion ' 17^ 17-22 — ' unquali- 
fied ')(' qualified' 17^32—19^5 
— cycHcal 31^ 23-^ 4 ; 37* 1-7 ; 
38* 4-^ 1 1 See also s. vv. 

Cause, Combination 

' Complementary factors ' (in the 
' simple ' bodies) 31=^ 23-^ 4 ; 
32^32-33; 32^29 

Compound bodies, how they come- 
to-be out of the ' simple ' bodies 
34*^8-30 — contain all four 
'simple' bodies 34^31—35*9 

— their food 35*9-14 
'Consecutive' 17*9: 31'' 4, 26, 

34; 37^ 35-'' I 
Contact 22^ 21 — 23^34 - of the 
' mathematical things ' 23^ 1-3 

— 'in general' )( 'recipro- 
cal ' 23*22-25 — ' of whole 
with whole ' 30^ 2 ' contacts ' 



(or ' points ', ' divisions ') 16'^ 4, 
7, 15 : 261^ 12 ; 27=^ 12 

Contrarieties, the 29^ 24 — 30^ 7 
(cf. 32^34-'^ 5) —primary 

tangible 29^^ 7 — 30^ 29 ' per- 
ceptible contrariety' 29* lo-ii 

Correspondence, terms in a 33=^ 

27-34 
Cyclical coming-to-be ^^7^ 1-7 ; 
■^^'^'^ 4-^11 — of the ' simple ' 
bodies 31^ 23-'^ 4 

Demokritos, quoted 26* 9 — 
praised for his method 15^ 34- 
^ I (cf.i6a 5-14 ; 24^ 35— 25*2j 

— denies the reality of Colour 
16^1-2 — maintains thatagent 
and patient must be 'like' 23^ 
10-15 — criticized 23^ 18-24 

— his theory abolishes 'altera- 
tion' and growth 27^ 15-25 
D. and Leukippos, their theory 
)( that of Anaxagoras 14^ 17- 
24 — postulate 'indivisible 

bodies ' ( = the ' Figures ') mov- 
ing in a ' void ', &;c. 14^^21-24; 
15^6-15; 15^28—16^1; 25* 
23-^5; 25b 13-19, 25-33 — 
criticized 25^34—26^6 (cf. 15^ 
6—17*31) — how their 

theory is related to Eleatic 
]Monism 24^ 35 — 25^ 5 

Dense and rare 30^9-13 (cf. 26* 
21-24) 

Diogenes of Apollonia 22^ 13-21 

' Discretes-in-contact ' 25^ 6-13 ; 
25^^ 5-1 1 

Dry-moist = a primary contrariety 
of touch 30* 24-29 — deriva- 
tive fonns of 29b 32— 30^^ 24 
the 'dry', defined 29^31-32 
dry and moist = differences 
characterizing the ' elements ' 
ofEmpedokles 14^17-26 

Duct (avXoy) used to illustrate the 
form of a growing tissue 22* 28- 

Earth, 'cold-dry' 30^^ 5 —par 
excellence 'dry ' 31* 4 — con- 
trary to Air 31* 2 ; 35^ 5-6 

— is an 'extreme' or 'end- 
element ' 30^> 33-34 ; 32'^ 5 ft". 

— and Fire in ' Parmenides ' 
18^ 2-7 ; 30'^ 14 ; (cf. 19* 29- 

33) 
Eleatic Monism, its relation to the 



INDEX 



theory of Leukippos and Demo- 
kritos 24^ 35—25^ 5 — criti- 
cized 25^ 13-23 

Elementary qualities (hot, cold, 
dry, moist) 30^ 30-'*' 7 ; 31*1- 
6 ; 31^ 26-36 

* Elements ', of Anaxagoras ( = the 
'homoeomeries') 14*^18-20; 14^ 
28-^1 — of Empedokles 14^ 
16-17, 26-27 ; 14^ 17-26 ; 15a 
19-25 ; 25^ 19-25 ; 29a 2-3 ; 
29^ 1-2; 30^ 19-21 ; 33^ 16- 
^3; 33*^20—34^2 —of Leu- 
kippos and Demokritos ( = the 
'Figures') 14^ 21-24; 15^6- 
15; 15^28—16^1; 25^23-^5; 
25b 13-19, 25-33 ; 25b 34—26^ 
6 — in Plato's theory, cf. 29* 

13-24 
— *the so-called' ( = the four 
'simple' bodies) 22^1-5; 28^ 
31 ; 29a 16, 26 ; 30^ 30-33* 15 ; 
34^ 15—35^ 23 — their con- 
stitution 29^24—31^6 — vari- 
ous modes in which they are 
transformed 31^ 7 — 32* 2 — 
cyclical transformation of 31' 



23- 



^ are similar to, but 



purer than, Air, Earth, Fire, 
and Water 30^21-30 — how 
theycombine to form compound 
bodies 34^ 8-30 — their 'na- 
tural ' )( ' compulsory ' move- 
ments 33^ 26-30 (cf. 35^ 14- 
21; 37^7-15) — their proper 
places or ' regions ' 30^ 30-33 ; 
34^34; 35'' 20-21; 37^-1 5 

— ' consecutive ' series of 31^ 
4, 26-36 

Empedokles, quoted 14^7, 20-22 ; 

33a 19-20 ; 33b 1-2, 14-15 ; 34a 

3,5 — parodied (?) 33^^ 15-16 

— criticized 14^4—15=^25 ; 25^ 

15-25; 26^6-28; 33=^16-34^2 

— his theory )( that of Anaxa- 
goras 1 4=^ 24-^ I — his theory 
of the ' elements ' 14^ 16-17 ; 
26-27; 14^17-26; 15=^19-25; 
25^ 19-25 ; 29a 2-3 ; 29^ 1-2 ; 
30^19-21; 33*16-^3; 33^20— 
34^2 

E. explains action-passion, com- 
bination, and perception by 
' pores ' 24^ 25-35 — thus 
' practically ' adopts ' the same 
theory as Leukippos' 25^1-11 
(cf. 25a 6-13) — gives a vague 



account of motion 33^ 22—34^ 9 

— fails to explain psychical 
changes 34* 9-15 

— his ' Love ' and ' Strife ' 14* 
17; 15^ 7. 17; 33^i2-34a9 
'The One' 15^ 6-25 'The 
Deity' 33^ 21 'The Mix- 

ture ' 34^ 28 (? cf. 27^ 19-22) 
'The Motion' 15*22 '^ Ether' 
( = Air)33^2; 34"- 1 "5 

' Environing ', the ( = the ' Bound- 
less ', q. V.) 32* 25 

' Eternal and primary things ' 35 * 
29 — their 'necessity ' 35* 33- 
^2 [ci.'il'^Z^—z'^^i) 

' Figures ', the (Leukippos and 
Demokritos) 15^7, 11; 26*4, 
6 ; 26b I 

Fire, ' hot-dry' 30^ 3-4 — par 
excelletice 'hot' 31* 5-6 (cf. 30^ 
25-30) — contrary to Water 
31a 1-2 ; 35a ^_5 _ is an ' ex- 
treme ' or ' end-element ' 30^33- 
34 ; 32^ 5 ff. — alone of all 
the ' simple ' bodies is ' fed ' 35 * 
14-20 — as an 'instrumental' 
cause 36* I-12 )( Earth in 

' Parmenides ' 18^ 2-7 ; 30^14 ; 
(cf. 19*29-33) 

Food 21*29-^ 10 ; 21^35 — 22*28 

— of compound bodies 35* 
9-14. 

Form = a ' positive predication ' 
)( privation 18^16-17 — and 
matter (in the growth of a tissue) 
21^16 - 22*4 ; 22* 28-33 — 
embodied in matter )( separate 
from matter 24^4-22 ' forms ' 
(i. e. ' ends ') = ' states ' 24^ 14- 
18 ' Forms ' and ' Partici- 

pants ' 35^ 9-24 

'Generator', the (=the sun) 36* 
18; (cf. 36^2-10, 15-19; -^^ 

1-5) 

God 36^ 27-34 

Growth (and diminution) 14^13- 
15; 15^1-3; 19^31-32; 20*8 — 
22*33; 25^3-5; 27*22-25 ~ 
differs from coming-to-be and 
' alteration ' in manner 20* 10- 
27 — of tissues' and 'organs' 
21^16—22*4 — dist. from 
nutrition 22* 20-28 — its 

three characteristics 21*2-5, 



INDEX 



17-29 — inexplicable on the 
theory of Empedokles 33^35-^^3 

Hard and soft 29^19; 30^8-12; 
(cf. 26^8, 13-14) = differences 
characterizing the ' elements ' 
of Empedokles 14^ 17-26 

Heavy and light 29^ 18-24 ; (cf. 
15^ II ; 19^ 29-33 ; 23=^ 6-12 ; 
26*6-11 ; 29* 11-12) 

Hot-cold = a primary contrariety 
of touch 30=^ 24-29 the ' hot ', 
defined 29^ 26-29 — a 'power 
to act ' 29^ 24-26 (cf. 30^ 12-13) 
— assigned to the spherical 
' figure ' by Demokritos 26^ 3- 
6, 9-12 hot and cold = differ- 
ences characterizing the " ele- 
ments ' of Empedokles 1 4*^ 1 7-26 

Identity, numerical )( specific 38^' 
6-19 

Indivisible magnitudes discussed 
15^24—17*17; (cf, 27*7-11; 
28*5-6) —bodies 14*21- 

24; 15^6-15, 29; 25*23-^5 ; 
25^ 13-19, 25-33 ; 25!^ 34—26^ 
6 — planes 15*^30— 16*4; 25^^ 
25-34 ; 26* 22 ; 29* 14-24 

Infinite, no 'actual' 18* 20-21 

— sequence contains no ' pri- 
mary ' member 37^ 25-29 

Irregular, coming-to-be 36^ 20-24 

— matter 36^ 21 — motion 
36* 30 ; 36^^ 5-6 

Leukippos 14*12; 25*23 — 
quoted (?) 25^4-5 — histheor)- 
comp. with that of Empedokles 
25^ i-li )( that of Plato 25^^ 
25-33 (cf. 15^' 28-33) See also 
s. V. Demokritos 

' Love ' and ' Strife' (Empedokles) 
14a 17; 15*7,17; 33^12—34*9 

Lynkeus 28* 15 

Vi.?^X^x [materia privia) 18* 2, 9, 
27; 19*17-22; 19*29-^^4; 20^ 
14-25 ; 28^ 33—29^ 5 ; 29* 24- 
35 ; 32^ 35-'^ I — q^i(^ matter, 
is 'passive' 24^' 18 (cf. 35^29- 
31) _ of the various form s of 
change 20* 2-5 ; 20^^ 22-25 — 
of growth 20* 27 ff. — i.q. 

perceptible material 18'' 14 — 
19a 3 (cf. 28'' 33) See also s.7'. 
'Elements' 



(Melissos) 25* 15-16 

Method, ' scientific' )( 'dialectical' 

16* 5-14; (cf. i5*34-b i; 35b 

24-29) 
' Moist', the, defined 29^ 30-31 ; 

(cf. 28*35-^4; 34^34-35^3) 
See also s.v. Dry-moist 

M otion, the primary form of change 
36* 18-23 — circular 37* i, 7, 
20-33 ; 38* 1 4-'^ 5 — eternal 
36* 15 ; 38* 18 — irregular 

36* 30 ; 36^ 5-6 ' the primar}^ 
motion ', ' the motion of the 
whole' 36*31; 36^3; 38*18- 
19 'the motion along the in- 
clined circle' 36* 31-^ 10 

' Movers ', unmoved )( moved 18* 
3-8 ; 23*12-33 ; 24*30-32 — 
comp. with agents 23* 12-22 ; 
24*24-^13 —'first' )( 'last' 
24* 26-32 

Nature always strives after 'the 

better ' 36^ 27-28 
Necessity, absolute )( conditional 

37b 1 0—38* 1 7 — and eternity 

37^33-38^3 
Nutrition dist. from growth 22* 
20-28 — assimilation in- 

volved in 21^35—22* 16 

Order, the, controlling all things 

36^12 (cf. -^-j^ 15) 
Organs grow by the growth of 

their tissues 21^ 16-19 

Parmenides (i. e. the doctrine 
expounded in the ' Way of 
Opinion ') 18^2-7 ; 30^ 13-15 
—the ' Way of Truth ', cf. 25* 
2-23 

Period, vital 36^' 10-15 

Place, primary differentiation of 
23*6-8 — 'position', 'con- 
proper 



tact' 22'' 32 — 23*25 



places or ' regions ' of the 
' simple ' bodies 30^ 30-33 ; 34^ 
34; 35*20-21 ; 37''' 7-1 5 
Plants, their food 35* 11- 14 
Plato 15* 29-33 ; 29* 13-24 ; 30^ 
16; 32*29-30 — his theory 
)( that of Leukippos 25^ 25-33 
(cf. 1 5^' 28-33) — his indi- 

visible planes 15^*30 — 16*4; 
25^25-34; 26*22; 29*14-24 
— his Timaeus 15^30; 25^' 
24; 29* 13; 32*29 — his'Di- 



INDEX 



visions' i^l =■ Timaeits 35^ ff.) 
30^ 16-17 — his Phaedo 35" 
9-24 ' The Omnirecipient ' 

29* 1 4-24 ' The Nurse ' 29* 23 
Points, cannot constitute a magni- 
tude 1 6* 25-34. — and lines 
not the matter of body 20^ 14- 

point, not 'immediately-next ' to 
point 17*2-12, 15-16 —'occu- 
pies ' no place 20^^ i — in 
what sense ' everywhere ' in a 
magnitude 17*^ 7-12 

Pores 24^25-35 ; 25^1-11; 26^ 
34 — criticized"^ 26^ 6-28 

' Powers of action ' 27^ 31 ; 28* 
28-31; 33"" 23-34; 37^3; (cf. 
34b 8-30) 

Privation )( positive predication 
(or 'a form') 18^ 16-17 

(Pythagorean) Materialists, their 
theory of coming-to-be 35^ 16- 
17; 35^24—36*12 

' Ouantum-in-general ' 22* 16-20 

Reality, degrees of, cf. 18^14 — 

19*3 
Rough and smooth 29^ 20 

' Sclera tes in the Phaedo\ para- 
phrased and criticized 35^ 9-24 

Time, infinite lapse of y]^ 9 — 
continuity of 37* 22-33 



Tissues, comp. to ' ducts ' 22* 28- 
33 (cf. also 21^3 24-25) — have 
'a twofold nature' 21^19-22 

— and organs 21'' 16-19, 28- 
32 

Veins of the 'susceptible ' 26^ 34 — 

27a I 
Viscous liquids 28^ 3-5 
Vision, prior to touch 29^ 14-16 

— explanation of, by ' pores ' 
24^ 25-32 ; 26*^ 10-14 

' Void ', cannot exist in separation 
from body 20^ 27-28 ; 21* 6-7 
= anon-perceptible body 20^2 
= a body's place 26^ 19 — 
denied by the Eleatics 25* 2-6 

— denied by Plato 25^ 33 

— supposed to exist (though un- 
real) by Leukippos 25*27-31 
(cf. 25^3-11, 31) 

Water, 'cold-moist '30^ 5 — par 
excellence ' cold '31* 4-5 — 
contrary to Fire 31* 1-2 ; 35* 
5-6 — is an intermediate 'ele- 
ment ' 30^34 31* I (cf. 30b 13- 
19; 32^10-12) — alone of 
the ' simple ' bodies is readily 
adaptable in shape 34'^ 35 — 
35'-^ I 

(Zeno) probably referred to 25* 2- 
23 



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